feat(trigger): DPLAN-0112 #4 — per-handler failure counting + auto-disable

_fire_to_handlers now tracks consecutive failures per handler. After 5
consecutive failures, the handler is auto-disabled (skipped) and a CRITICAL
log is emitted. Success resets the failure count. Disabled handlers re-enable
on process restart (in-memory tracking). Prevents broken handlers from
flooding logs forever. 370 tests passing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/aipass/trigger/apps/modules/core.py

@@ -48,6 +48,9 @@ class Trigger:
     _deferred_queue = []  # Queue for events fired during handling
     _draining_deferred = False  # Prevents nested deferred processing
     _log_watcher_started = False  # Lazy-start flag for log watcher
+    _handler_failures = {}  # handler -> consecutive failure count
+    _disabled_handlers = set()  # handlers auto-disabled after repeated failures
+    _HANDLER_FAILURE_THRESHOLD = 5  # consecutive failures before auto-disable
 
     @classmethod
     def _ensure_initialized(cls):
@@ -99,10 +102,22 @@ class Trigger:
         data = dict(data)  # Copy to avoid mutating caller's dict
         data['fire_event'] = cls.fire
         for handler in handlers:
+            if handler in cls._disabled_handlers:
+                continue
             try:
                 handler(**data)
+                cls._handler_failures.pop(handler, None)  # Reset on success
             except Exception as e:
-                logger.error(f"[TRIGGER] Handler error for {event}: {e}")
+                count = cls._handler_failures.get(handler, 0) + 1
+                cls._handler_failures[handler] = count
+                if count >= cls._HANDLER_FAILURE_THRESHOLD:
+                    cls._disabled_handlers.add(handler)
+                    logger.error(
+                        f"[TRIGGER] Handler {getattr(handler, '__name__', handler)} "
+                        f"disabled after {count} consecutive failures"
+                    )
+                else:
+                    logger.error(f"[TRIGGER] Handler error for {event}: {e}")
 
     @classmethod
     def _drain_deferred(cls) -> None: