feat: extract in-process MCP action layer, concurrent task dispatch, and spawn/reconcile hardening

- Extract device action execution into artemis/mcp action layer:
  typed ActionResult, capability manifest with startup validation,
  AdbActuator as the single physical implementation, in-memory
  ActionSession (replaces stdio subprocess MCP in validator), and
  McpActionExecutor preserving the legacy executor contract.
  adb_server keeps its external stdio/SSE surface unchanged and now
  reuses the actuator implementation; import-time side effects moved
  into configure_stdio_mode().
- Capability-gated prompt assembly (prompt_assembly.py): tool enums and
  teaching segments render per available backend tools; full-set output
  is byte-identical to the previous static text (locked by tests).
- Admin console task queue: serial worker replaced by a per-device
  concurrent dispatcher (ARTEMIS_CONCURRENCY_MODE=global restores
  serial semantics), per-session cancellation, strict device binding on
  enqueue, unified stdio piping with tee to trace stdout.log, and
  shutdown cleanup of all active runs. Fix _pid_exists exception order
  so PermissionError is treated as alive.
- mcp_server reliability: spawn watchdog kills runners stuck before
  interpreter startup and releases device reservations; task state
  reconcile uses psutil liveness, prefers runner-reported pids, and
  adds a 45s startup grace to stop false failure reports on Windows;
  conversation_id is now optional end-to-end; explicit device_serial is
  validated at submission.
- CLI install now writes ~/.claude/rules/artemis.md for Claude Code and
  migrates/removes the legacy CLAUDE.md injection block; ~/.claude.json
  is never rewritten when it fails to parse.
- Tests: Windows-portable stdio lifecycle and path assertions; new
  suites for action layer, prompt assembly, spawn watchdog, and task
  reconcile (895 passed, 3 skipped).

artemis/mcp/action_session.py

@@ -0,0 +1,249 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""In-process MCP session over the unified action server.
+
+The in-memory transport (``create_connected_server_and_client_session``) wraps the
+server in an ``anyio`` task group whose cancel scope must be entered and exited **in
+the same task**. ``ActionSession`` therefore runs the whole context manager inside one
+owner task and communicates through events: ``call()`` and ``aclose()`` are safe from
+any task, which is what lets the session be created lazily inside an agent node and
+torn down from ``ArtemisContext.__aexit__``.
+
+Transport operations additionally run **only in the owner task**, via a request
+queue: callers enqueue ``(future, name, args, timeout)`` and await the future. A
+caller that times out or is cancelled only abandons its future -- the underlying
+``call_tool`` is never cancelled mid-flight. This matters because cancelling
+``call_tool`` on the in-memory transport corrupts the shared memory streams and
+bricks the session for every subsequent caller (observed live: one 1-second
+``asyncio.wait_for`` around a slow hierarchy fetch killed a 24-minute run, with
+every later call failing on an empty-message ``BrokenResourceError``).
+
+MCP's native ``read_timeout_seconds`` is just as fatal here (also observed live):
+mcp 1.29's ``_handle_response`` delivers a LATE response into the timed-out
+request's already-closed response stream, which crashes the client receive loop.
+Per-call timeouts therefore travel as a ``timeout_ms`` tool argument and fire
+inside the server tool, around the actuator call only -- a timed-out operation
+produces a normal error payload and never a late response.
+
+If the transport does die despite all this, the owner loop exits, which flips
+``started`` to False so the next ``get_action_session`` builds a fresh session
+instead of leaving the rest of the run to fail on a corpse.
+
+The single owner loop also serializes calls, which enforces ARTEMIS's
+single-device policy at the one choke point all agents share -- in particular it
+stops a nested Validator -> FailureAnalyzer flow from interleaving two device
+actions.
+"""
+
+import asyncio
+from typing import Any
+
+import anyio
+from mcp.shared.memory import create_connected_server_and_client_session
+
+from artemis.mcp.action_types import ActionResult, ObserveResult
+from artemis.utils.logger import get_logger
+
+logger = get_logger(__name__)
+
+__all__ = ["ActionSession", "get_action_session"]
+
+_SHUTDOWN = object()  # queue sentinel
+
+
+class ActionSession:
+    """Owns the in-memory MCP client/server pair for one device run."""
+
+    def __init__(self, server: Any):
+        self._server = server
+        self._session: Any = None
+        self._ready = asyncio.Event()
+        self._owner: asyncio.Task | None = None
+        self._error: BaseException | None = None
+        self._requests: asyncio.Queue = asyncio.Queue()
+
+    async def _run(self) -> None:
+        try:
+            # Enter and exit strictly within this task (anyio cancel-scope rule).
+            async with create_connected_server_and_client_session(self._server) as session:
+                self._session = session
+                self._ready.set()
+                await self._serve(session)
+        except BaseException as e:
+            self._error = e
+            self._ready.set()
+            raise
+        finally:
+            self._session = None
+            self._fail_pending("ActionSession owner task has exited.")
+
+    async def _serve(self, session: Any) -> None:
+        """Executes queued transport calls until the shutdown sentinel arrives."""
+        while True:
+            item = await self._requests.get()
+            if item is _SHUTDOWN:
+                return
+            fut, name, args = item
+            if fut.cancelled():
+                continue  # caller gave up before we started; nothing was sent
+            try:
+                result = await session.call_tool(name, args)
+            except BaseException as e:
+                if not fut.cancelled():
+                    fut.set_exception(e)
+                if isinstance(e, asyncio.CancelledError):
+                    raise
+                if isinstance(e, (anyio.ClosedResourceError, anyio.BrokenResourceError)):
+                    # The transport is dead; no future call on this session can
+                    # succeed. Exit so `started` flips False and the next
+                    # get_action_session() builds a fresh session.
+                    logger.error(
+                        "Action session transport failed (%r); retiring this session.", e
+                    )
+                    return
+            else:
+                if not fut.cancelled():
+                    fut.set_result(result)
+
+    def _fail_pending(self, reason: str) -> None:
+        while not self._requests.empty():
+            item = self._requests.get_nowait()
+            if item is _SHUTDOWN:
+                continue
+            fut = item[0]
+            if not fut.done():
+                fut.set_exception(RuntimeError(reason))
+
+    async def start(self) -> "ActionSession":
+        if self._owner is not None:
+            return self
+        self._owner = asyncio.create_task(self._run(), name="artemis-action-session")
+        await self._ready.wait()
+        if self._error is not None:
+            error = self._error
+            self._owner = None
+            self._error = None
+            raise RuntimeError(f"Failed to start action session: {error}") from error
+        return self
+
+    @property
+    def started(self) -> bool:
+        return self._session is not None
+
+    async def call_raw(self, name: str, args: dict[str, Any]) -> Any:
+        """Calls a tool and returns the raw ``CallToolResult``.
+
+        There is deliberately no transport-level timeout here (see the module
+        docstring). Tools that support one take a ``timeout_ms`` argument and time
+        out server-side. Wrapping this coroutine in ``asyncio.wait_for`` merely
+        abandons the caller's future -- harmless, because the transport call itself
+        runs in the owner task and cannot be cancelled from here.
+        """
+        if self._session is None:
+            raise RuntimeError("ActionSession is not started.")
+        fut: asyncio.Future = asyncio.get_running_loop().create_future()
+        self._requests.put_nowait((fut, name, args))
+        result = await fut
+        if getattr(result, "isError", False):
+            # Protocol-level failure (unknown tool, schema violation) -- a programming
+            # error, not a device observation.
+            text = ""
+            for block in getattr(result, "content", []) or []:
+                if getattr(block, "type", None) == "text":
+                    text = block.text
+                    break
+            raise RuntimeError(f"MCP tool '{name}' failed: {text}")
+        return result
+
+    async def call(self, name: str, args: dict[str, Any]) -> ActionResult:
+        """Calls a device action tool and returns its typed result."""
+        result = await self.call_raw(name, args)
+        return ActionResult.model_validate(result.structuredContent)
+
+    async def observe(
+        self, settle_ms: int = 400, include_image: bool = False
+    ) -> ObserveResult:
+        """Captures and indexes the current screen via the internal observe tool."""
+        result = await self.call_raw(
+            "observe_screen", {"settle_ms": settle_ms, "include_image": include_image}
+        )
+        return ObserveResult.model_validate(result.structuredContent)
+
+    async def screenshot_b64(self, timeout: float | None = None) -> str:
+        """Returns the current screen as a base64 string (no persistence)."""
+        args = {"timeout_ms": int(timeout * 1000)} if timeout else {}
+        result = await self.call_raw("take_screenshot", args)
+        payload = result.structuredContent or {}
+        # FastMCP wraps plain-dict returns as {"result": ...} only for non-dict types;
+        # dicts pass through.
+        data = payload.get("result", payload)
+        if not data.get("ok"):
+            raise RuntimeError(f"take_screenshot failed: {data.get('error')}")
+        return data["image_b64"]
+
+    async def ui_hierarchy(self, timeout: float | None = None) -> Any:
+        """Returns the raw UI element hierarchy."""
+        args = {"timeout_ms": int(timeout * 1000)} if timeout else {}
+        result = await self.call_raw("get_ui_hierarchy", args)
+        payload = result.structuredContent or {}
+        data = payload.get("result", payload)
+        if not data.get("ok"):
+            raise RuntimeError(f"get_ui_hierarchy failed: {data.get('error')}")
+        return data["elements"]
+
+    async def aclose(self) -> None:
+        """Shuts the session down; safe to call from any task."""
+        if self._owner is None:
+            return
+        self._requests.put_nowait(_SHUTDOWN)
+        try:
+            await asyncio.wait_for(asyncio.shield(self._owner), timeout=5.0)
+        except (TimeoutError, asyncio.CancelledError, Exception) as e:
+            logger.warning(f"Action session owner task did not exit cleanly: {e!r}")
+        finally:
+            self._owner = None
+            self._ready = asyncio.Event()
+
+
+async def get_action_session(ctx: Any, actuator: Any = None) -> ActionSession:
+    """Returns the context's action session, creating and starting it on first use.
+
+    Contract validation happens here (inside ``build_action_server``), so a backend
+    that cannot satisfy the manifest fails before the first device interaction.
+    """
+    existing = getattr(ctx, "action_session", None)
+    if existing is not None and existing.started:
+        return existing
+    if existing is not None:
+        # A dead session still owns a task and memory streams: release them
+        # before the replacement is built.
+        try:
+            await existing.aclose()
+        except Exception:
+            logger.debug("Closing a dead action session failed; replacing it anyway.")
+
+    from artemis.mcp.action_server import build_action_server
+    from artemis.mcp.actuators.adb import AdbActuator
+
+    actuator = actuator or getattr(ctx, "actuator", None) or AdbActuator(ctx)
+    server = build_action_server(actuator)
+    session = ActionSession(server)
+    await session.start()
+    try:
+        ctx.action_session = session
+    except Exception:
+        # Contexts that forbid new attributes (strict mocks) can still use the session.
+        logger.debug("Could not store action session on ctx; proceeding unattached.")
+    return session