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).

apps/admin_console/routers/tasks.py

@@ -103,10 +103,15 @@ async def run_task(request: RunRequest):
 
     if device_probe and device_probe.metadata.get("active_device"):
         verified_serial = device_probe.metadata["active_device"].get("serial")
-        if verified_serial:
+        # Only auto-selected targets may be re-bound to the probed device. An
+        # explicitly requested serial is never silently replaced -- if it is
+        # invalid, enqueue_tasks rejects the submission with a clear error.
+        if verified_serial and not request.device_serial:
             target_serial = verified_serial
-            if readiness_engine.get_active_device_serial() != verified_serial:
-                readiness_engine.set_active_device_serial(verified_serial)
+        # The probe verified a live device either way: keep the global active
+        # serial in sync even when the caller pinned the target explicitly.
+        if verified_serial and readiness_engine.get_active_device_serial() != verified_serial:
+            readiness_engine.set_active_device_serial(verified_serial)
 
     return await task_queue_service.enqueue_tasks(
         incoming_goals,