test: Added integration tests for the sub-agent spawning system and inter-agent communication mechanisms

docs/testing/plans/11-sub-agent-spawning.md

@@ -10,50 +10,71 @@ to request user input through the parent.
 ## Behaviors to test
 
 ### Spawn
-- [ ] agent__spawn creates child agent in background (integration)
-- [ ] Child gets own RequestContext with incremented depth (integration)
-- [ ] Child gets own session, model, functions (integration)
-- [ ] Child gets shared root_escalation_queue (integration)
-- [ ] Child gets inbox for teammate messaging (integration)
-- [ ] Child MCP servers acquired if configured (integration)
+- [ ] agent__spawn creates child agent in background (requires agent config on disk)
+- [x] Child gets own RequestContext with incremented depth (new_for_child)
+- [x] Child starts with empty scope (new_for_child)
+- [x] Child gets shared root_escalation_queue (new_for_child)
+- [x] Child gets inbox for teammate messaging (new_for_child)
+- [x] Child inherits parent_supervisor (new_for_child)
+- [ ] Child MCP servers acquired if configured (requires live MCP)
 - [x] Max concurrent agents enforced (Supervisor.register)
 - [x] Max depth enforced (Supervisor.register)
-- [ ] Agent not found → error (integration)
-- [ ] can_spawn_agents=false → no spawn tools available (integration)
+- [ ] Agent not found → error (requires agent config on disk)
+- [ ] can_spawn_agents=false → no spawn tools available (requires agent init)
 
 ### Collect/Check
-- [ ] agent__check returns PENDING or result (integration)
-- [ ] agent__collect blocks until done, returns output (integration)
-- [ ] Output summarization when exceeds threshold (integration)
-- [ ] Summarization uses configured model (integration)
+- [x] agent__check returns PENDING for running agent
+- [x] agent__check returns error for unknown agent
+- [ ] agent__collect blocks until done, returns output (requires real child completion)
+- [ ] Output summarization when exceeds threshold (requires LLM client)
+- [ ] Summarization uses configured model (requires LLM client)
 
-### Task queue
-- [x] agent__task_create creates tasks with dependencies
-- [x] agent__task_complete marks done, unblocks dependents
-- [x] Auto-dispatch agent/prompt stored on task
-- [x] agent__task_list shows all tasks with status
+### Task queue (handler integration tests)
+- [x] handle_task_create creates tasks (simple, with deps, with dispatch_agent)
+- [x] handle_task_create errors when agent set without prompt
+- [x] handle_task_complete unblocks dependents
+- [x] handle_task_list shows all tasks
+- [x] handle_task_fail marks failed and reports blocked dependents
+- [x] handle_task_fail returns error for missing task
 
-### Escalation
-- [x] Escalation submitted and retrievable
+### Escalation (handler integration tests)
+- [x] handle_reply_escalation delivers reply via oneshot channel
+- [x] handle_reply_escalation errors for missing escalation_id
+- [x] handle_reply_escalation errors when no queue
 - [x] Pending summary contains correct fields
 - [x] Reply reaches receiver via oneshot channel
-- [ ] Escalation timeout → fallback message (integration)
+- [ ] Escalation timeout → fallback message (requires tokio timeout)
 
-### Teammate messaging
-- [x] Deliver to inbox
-- [x] Drain empties inbox
-- [x] Drain ordering: shutdown > task_completed > text
+### Teammate messaging (handler integration tests)
+- [x] handle_send_message delivers to registered agent's inbox
+- [x] handle_send_message errors for unknown agent
+- [x] handle_check_inbox returns messages with count
+- [x] handle_check_inbox returns empty when no inbox
+- [x] handle_check_inbox returns empty for empty inbox
+
+### Cancel/List (handler integration tests)
+- [x] handle_list returns empty for fresh supervisor
+- [x] handle_list returns registered agents
+- [x] handle_list errors when no supervisor
+- [x] handle_cancel removes agent and signals abort
+- [x] handle_cancel errors for unknown agent
+- [x] handle_cancel errors when no supervisor
+
+### Dispatch routing
+- [x] Unknown action → error with "Unknown supervisor action"
+- [x] agent__list routes to handle_list
+- [x] agent__task_list routes to handle_task_list
 
 ### Child agent lifecycle
-- [ ] run_child_agent loops (integration)
-- [ ] Child uses before/after_chat_completion (integration)
-- [ ] Child tool calls evaluated (integration)
-- [ ] Child exits cleanly (integration)
+- [ ] run_child_agent loops (requires LLM client)
+- [ ] Child uses before/after_chat_completion (requires LLM client)
+- [ ] Child tool calls evaluated (requires LLM client)
+- [ ] Child exits cleanly (requires LLM client)
 
 ## Context switching scenarios
-- [ ] Parent spawns child with MCP (integration)
-- [ ] Parent exits agent → all children cancelled (integration)
-- [ ] Multiple children share escalation queue correctly (integration)
+- [ ] Parent spawns child with MCP (requires live MCP + agent config)
+- [ ] Parent exits agent → all children cancelled (requires agent init)
+- [x] Multiple children share escalation queue (new_for_child + ensure_root_escalation_queue)
 
 ## Additional behaviors tested (not in original plan)
 
@@ -73,6 +94,13 @@ to request user input through the parent.
 - [x] TaskQueue: dependency on nonexistent errors, complete nonexistent
 - [x] TaskNode: is_runnable when pending+unblocked, not when blocked
 
+## Integration handler tests added
+
+- [x] All handle_* functions tested via handler integration tests (36 tests)
+- [x] new_for_child: depth, id, inbox, escalation queue, parent supervisor, empty scope
+- [x] ensure_root_escalation_queue: lazy init, same Arc on repeated calls
+- [x] AppState::test_default() helper added for cross-module test construction
+
 ## Old code reference
 - `src/function/supervisor.rs` — all handler functions
 - `src/supervisor/` — Supervisor, EscalationQueue, Inbox, TaskQueue