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).

tests/unit/mcp/test_trace_store.py

@@ -14,6 +14,7 @@
 
 """Unit tests for MCP trace store."""
 
+import os
 import shutil
 import tempfile
 import uuid
@@ -80,6 +81,6 @@ def test_read_nonexistent_status(temp_trace_env):
 def test_trace_paths(temp_trace_env):
     trace_id = "test-paths-id"
     trace_dir = trace_store.get_trace_dir(trace_id)
-    assert trace_store.get_trace_notes_dir(trace_id) == f"{trace_dir}/notes"
-    assert trace_store.get_trace_stdout_log_path(trace_id) == f"{trace_dir}/stdout.log"
-    assert trace_store.get_trace_stderr_log_path(trace_id) == f"{trace_dir}/stderr.log"
+    assert trace_store.get_trace_notes_dir(trace_id) == os.path.join(trace_dir, "notes")
+    assert trace_store.get_trace_stdout_log_path(trace_id) == os.path.join(trace_dir, "stdout.log")
+    assert trace_store.get_trace_stderr_log_path(trace_id) == os.path.join(trace_dir, "stderr.log")