feat(agent): add manage_bg_jobs tool to inspect and kill background bash jobs (#4577)

Detached bash jobs (#!bg) could be launched and auto-reported on completion,
but the agent had no way to act on a running one: no on-demand output read and
no kill (it blocked until the 1h max-runtime). bg_jobs had the pieces
(_read_output, list_for_session, internal _kill) but none was exposed.

Adds:
- bg_jobs.kill(job_id): tears down the process tree, marks the job killed, and
  sets followed_up so the monitor does not also auto-continue a deliberate kill.
- manage_bg_jobs registry tool with actions list / output / kill, scoped to the
  chat that launched the job (cross-session access reads as not found).
- Wiring: TOOL_HANDLERS/TAGS, function schema, RAG index + keyword hints, parser
  name map, dispatch (threads session_id via _direct_fallback). Gated like bash
  (NON_ADMIN_BLOCKED_TOOLS; plan-mode mutator).
- agent_loop: background-job intent regex maps to the files domain (and the tool
  joins _DOMAIN_TOOL_MAP[files]) so short commands like 'kill that job' are not
  dropped by the low-signal gate that skips tool retrieval.
- bg launch message tells the model to call manage_bg_jobs itself for check/stop
  rather than printing raw tool syntax to the user.

Tests: tests/test_bg_job_tools.py (kill semantics, per-chat scoping, actions,
and the intent classifier).

src/agent_loop.py

@@ -281,7 +281,7 @@ _DOMAIN_TOOL_MAP = {
     "notes_calendar_tasks": {"manage_notes", "manage_calendar", "manage_tasks"},
     "ui": {"ui_control"},
     "sessions": {"create_session", "list_sessions", "manage_session", "send_to_session", "search_chats"},
-    "files": {"bash", "python", "read_file", "write_file", "edit_file", "grep", "glob", "ls", "get_workspace"},
+    "files": {"bash", "python", "read_file", "write_file", "edit_file", "grep", "glob", "ls", "get_workspace", "manage_bg_jobs"},
     "settings": {"manage_settings", "manage_endpoints", "manage_mcp", "manage_webhooks", "manage_tokens", "app_api"},
     "contacts": {"resolve_contact", "manage_contact"},
     "integrations": {"api_call"},
@@ -816,6 +816,12 @@ def _classify_agent_request(messages: List[Dict], last_user: str) -> Dict[str, o
         domains.add("sessions")
     if has(r"\b(file|folder|directory|repo|git|grep|find in files|read file|edit file|shell|terminal|bash|python)\b"):
         domains.add("files")
+    # Managing detached bash jobs: "kill the background job", "stop the job",
+    # "kill that job", "check the job output", "is the bg job done".
+    if (has(r"\b(background|bg)\s+(jobs?|task)\b")
+            or has(r"\b(kill|stop|cancel|terminate|check|tail|show|list)\b.{0,16}\bjobs?\b")
+            or has(r"\bjobs?\b.{0,16}\b(output|status|done|finished|running)\b")):
+        domains.add("files")
     if has(r"\b(endpoint|api token|mcp|webhook|preference|configure|config|setting)\b"):
         domains.add("settings")
     if has(r"\b(contact|contacts|phone|phone number|address book|vcard)\b"):