feat: multi-level agent management — background agents, lifecycle tools, 3-level hierarchy

agent_manager.py (new):
- AgentRecord dataclass: agent_id, level (1/2/3), role, task, status, started,
  parent_id (lineage), finished, result, notify, _task_ref
- register() / finish() / cancel_agent() / list_agents() / get() / set_task_ref()
- Calls notification.notify() on completion when notify=True (same channel as
  reminders and cron completions)
- 24-hour pruning of completed records on each new registration

spawn_agent (tools/agents.py):
- background=True: fires asyncio.create_task(), registers in agent_manager, returns
  agent_id string immediately — sync path unchanged (no regression)
- notify=True: push/Talk notification when the background task completes
- Level enforcement: _agent_level param tracks hierarchy depth; when spawning from
  Level 2, child automatically gets spawn_agent + aider_run denied so Level 3 agents
  cannot delegate further

New lifecycle tools (tools/agents.py + __init__.py):
- agent_status(agent_id) — status, role, level, elapsed, task, result preview; user-level
- agent_list(status, limit) — all agents for current user, newest first; user-level
- agent_cancel(agent_id) — kills background task; admin-only, confirm-required

tests/test_agent_manager.py (new, 41 tests):
- agent_manager CRUD, pruning, notification hook
- spawn_agent background: returns immediately, completes async, timeout, failure
- Level enforcement: L1→L2 permits spawn, L2→L3 auto-denies; explicit tool_list path
- agent_status / agent_list / agent_cancel output formatting
- aider_run background: returns agent_id, completes async, sync path unchanged
- All tests run without browser or Cortex service (~2.5s total)
  Run: cd cortex && .venv/bin/python -m pytest tests/test_agent_manager.py -v

Docs: ARCH__FUTURE.md §13 (full design), ROADMAP.md, TODO__Agents.md, MASTER.md,
HELP.md (orchestrator description corrected, tool schema line updated to reflect
keyword routing), CLAUDE.md tool count 66→69.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -281,7 +281,7 @@ Cortex is running and stable. All channels are live:
 
 Active users: scott (inara), holly (tina), brian (wintermute)
 
-**65 orchestrator tools** across 17 domain modules:
+**69 orchestrator tools** across 17 domain modules:
 web_search/http_fetch/web_read/http_post,
 project_file_read/list + file_stat/grep/diff/syntax_check (project-scoped),
 file_read/list/write/session_read/session_search (system-scoped, admin),
@@ -293,7 +293,8 @@ reminders_add/list/remove/clear, scratch_read/write/append/clear,
 web_push/email_send/nc_talk_send/nc_talk_history,
 ae_journal_list/search/entries_list/entry_read/create/update/disable/append/prepend,
 ae_task_list, ae_db_query/describe/show_view (SELECT-only MariaDB access, admin; disable requires confirm),
-agent_notes_read/write/append/clear, spawn_agent,
+agent_notes_read/write/append/clear, spawn_agent/aider_run (admin; aider_run requires confirm),
+agent_status/agent_list (user-level)/agent_cancel (admin, confirm-required),
 ha_get_state/ha_get_states/ha_call_service.
 
 Each tool has a `TOOL_RISK` rating (low/medium/high). Configure access at `/settings/tools`