fix(tui): autonomous background process completion notifications (#26071) (#26327)

* feat(process-registry): add format_process_notification shared helper

* feat(process-registry): add drain_notifications method

* refactor(cli): use shared drain_notifications and format_process_notification

* feat(tui): add background notification poller for completion_queue

* feat(tui): wire notification poller into session init/finalize

* refactor(tui): add post-turn drain using shared helper as safety net

tests/tools/test_process_registry.py

@@ -865,3 +865,138 @@ class TestProcessToolHandler:
         from tools.process_registry import _handle_process
         result = json.loads(_handle_process({"action": "unknown_action"}))
         assert "error" in result
+
+
+# =========================================================================
+# format_process_notification + drain_notifications (shared helpers)
+# =========================================================================
+
+from tools.process_registry import format_process_notification
+
+
+def test_format_completion_event():
+    evt = {
+        "type": "completion",
+        "session_id": "proc_abc",
+        "command": "sleep 5",
+        "exit_code": 0,
+        "output": "done",
+    }
+    result = format_process_notification(evt)
+    assert "[IMPORTANT: Background process proc_abc completed" in result
+    assert "exit code 0" in result
+    assert "Command: sleep 5" in result
+    assert "Output:\ndone]" in result
+
+
+def test_format_watch_match_event():
+    evt = {
+        "type": "watch_match",
+        "session_id": "proc_xyz",
+        "command": "tail -f log",
+        "pattern": "ERROR",
+        "output": "ERROR: disk full",
+        "suppressed": 0,
+    }
+    result = format_process_notification(evt)
+    assert 'watch pattern "ERROR"' in result
+    assert "Matched output:\nERROR: disk full" in result
+
+
+def test_format_watch_match_with_suppressed():
+    evt = {
+        "type": "watch_match",
+        "session_id": "proc_xyz",
+        "command": "tail -f log",
+        "pattern": "WARN",
+        "output": "WARN: low mem",
+        "suppressed": 3,
+    }
+    result = format_process_notification(evt)
+    assert "3 earlier matches were suppressed" in result
+
+
+def test_format_watch_disabled_event():
+    evt = {
+        "type": "watch_disabled",
+        "message": "Watch disabled for proc_xyz: too many matches",
+    }
+    result = format_process_notification(evt)
+    assert "[IMPORTANT: Watch disabled for proc_xyz" in result
+
+
+def test_format_returns_none_for_empty_event():
+    evt = {}
+    result = format_process_notification(evt)
+    assert result is not None
+    assert "unknown" in result
+
+
+def test_drain_notifications_returns_pending_events():
+    from tools.process_registry import process_registry
+
+    while not process_registry.completion_queue.empty():
+        process_registry.completion_queue.get_nowait()
+
+    process_registry.completion_queue.put({
+        "type": "completion",
+        "session_id": "proc_drain1",
+        "command": "echo hi",
+        "exit_code": 0,
+        "output": "hi",
+    })
+    process_registry.completion_queue.put({
+        "type": "watch_match",
+        "session_id": "proc_drain2",
+        "command": "tail -f x",
+        "pattern": "ERR",
+        "output": "ERR found",
+        "suppressed": 0,
+    })
+
+    try:
+        results = process_registry.drain_notifications()
+        assert len(results) == 2
+        assert results[0][0]["session_id"] == "proc_drain1"
+        assert "proc_drain1 completed" in results[0][1]
+        assert results[1][0]["session_id"] == "proc_drain2"
+        assert "watch pattern" in results[1][1]
+    finally:
+        while not process_registry.completion_queue.empty():
+            process_registry.completion_queue.get_nowait()
+        process_registry._completion_consumed.discard("proc_drain1")
+        process_registry._completion_consumed.discard("proc_drain2")
+
+
+def test_drain_notifications_skips_consumed():
+    from tools.process_registry import process_registry
+
+    while not process_registry.completion_queue.empty():
+        process_registry.completion_queue.get_nowait()
+
+    process_registry._completion_consumed.add("proc_consumed")
+    process_registry.completion_queue.put({
+        "type": "completion",
+        "session_id": "proc_consumed",
+        "command": "echo done",
+        "exit_code": 0,
+        "output": "done",
+    })
+
+    try:
+        results = process_registry.drain_notifications()
+        assert len(results) == 0
+    finally:
+        process_registry._completion_consumed.discard("proc_consumed")
+        while not process_registry.completion_queue.empty():
+            process_registry.completion_queue.get_nowait()
+
+
+def test_drain_notifications_empty_queue():
+    from tools.process_registry import process_registry
+
+    while not process_registry.completion_queue.empty():
+        process_registry.completion_queue.get_nowait()
+
+    results = process_registry.drain_notifications()
+    assert results == []