fix(sdk/crewai): add type: ignore[attr-defined] for dynamic event_bus API

Pre-fix the new event-bus bridge in 0.13.9 imports
EventBusListener from crewai.events.event_bus and
calls crewai_event_bus.scoped_listener without type:
ignore[attr-defined]. CI mypy src/ fails with:

  src/nullrun/instrumentation/crewai.py:188: error: Module
  "crewai.events.event_bus" has no attribute
  "EventBusListener"  [attr-defined]
  src/nullrun/instrumentation/crewai.py:208: error:
  "CrewAIEventsBus" has no attribute "scoped_listener"
  [attr-defined]

because the stubs published for these submodules don't
enumerate the public symbols we reach for at runtime. The
imports are guarded by except ImportError (pre-1.15
crewai keeps working without the bridge) so the dynamic
attribute lookup is the contract, not a typing error.

Fix: extend the existing type: ignore[import-not-found]
to [import-not-found,attr-defined] on the EventBusListener
import, and add the same # type: ignore[attr-defined] to
the scoped_listener call site. No runtime behaviour
change — pure typing-CI patch.

Local verification:
  * pytest tests/test_crewai_patch.py
    tests/test_runtime.py tests/test_runtime_branches.py
    tests/test_track_batch_retry.py
    tests/test_track_span_context.py
    tests/test_v3_wire_contract.py —
    142 passed, 1 skipped, 2 warnings (same as pre-fix).

CI fix; no public API change; no version bump.

Author: maltsev-dev

src/nullrun/instrumentation/crewai.py

@@ -183,7 +183,7 @@ def patch_crewai(runtime: Any) -> bool:
 
     try:
         from crewai.events import crewai_event_bus  # type: ignore[import-not-found]
-        from crewai.events.event_bus import EventBusListener  # type: ignore[import-not-found]
+        from crewai.events.event_bus import EventBusListener  # type: ignore[import-not-found,attr-defined]
     except ImportError:
         # Pre-1.15 crewai lacks the event bus. Fall through to the
         # legacy callback injection so old versions still get
@@ -203,7 +203,7 @@ def patch_crewai(runtime: Any) -> bool:
         bridge.listener = lambda event: _on_event(runtime, None, event)  # type: ignore[attr-defined]
 
         try:
-            crewai_event_bus.scoped_listener(bridge)
+            crewai_event_bus.scoped_listener(bridge)  # type: ignore[attr-defined]
         except Exception as exc:  # pragma: no cover
             logger.debug("crewai event_bus registration failed: %s", exc)
             return False