fix: make get_info_for_dispatch abstract to prevent silent notification drops

[ez-lbz]

What changed

1. Make get_info_for_dispatch abstract on PushNotificationConfigStore

Problem: PushNotificationConfigStore.get_info_for_dispatch() (src/a2a/server/tasks/push_notification_config_store.py) was not @abstractmethod. Its default implementation fell back to get_info(task_id, ServerCallContext()) with a synthetic empty context, which resolves to the empty-string owner partition and returns no configs — silently dropping every push notification in any deployment with multiple owners. A subclass that forgot to override the method only logged a warning per call, so the failure was easy to miss in production.

Fix (src/a2a/server/tasks/push_notification_config_store.py):

• get_info_for_dispatch() is now @abstractmethod; the silent owner-scoped fallback is removed. Any store implementation that does not provide the cross-owner dispatch read path now fails loudly at instantiation time instead of dropping notifications at runtime.
• Removed the now-unused module-level logger.
• Verified both built-in stores already implement the method: InMemoryPushNotificationConfigStore (inmemory_push_notification_config_store.py) and DatabasePushNotificationConfigStore (database_push_notification_config_store.py).

Testing

• ./.venv/Scripts/python -m pytest tests/server/tasks/test_inmemory_push_notifications.py -q → 20 passed (includes 2 new tests: an incomplete subclass without get_info_for_dispatch cannot be instantiated; both built-in stores expose a callable dispatch read path).
• ./.venv/Scripts/python -m pytest tests/server/tasks/test_database_push_notification_config_store.py -q → 23 passed, 44 skipped (skips are DB-DSN-dependent tests, pre-existing).
• ./.venv/Scripts/python -m ruff check on modified files: clean.
• Behavior change: third-party subclasses of PushNotificationConfigStore that do not implement get_info_for_dispatch will now raise TypeError at instantiation instead of silently dropping notifications. This is the intended loud-failure hardening.

[github-actions]

🧪 Code Coverage (vs main)

⬇️ Download Full Report

	Base	PR	Delta
src/a2a/server/events/event_queue_v2.py	91.79%	91.28%	🔴 -0.51%
src/a2a/server/tasks/push_notification_config_store.py	60.00%	100.00%	🟢 +40.00%
src/a2a/utils/telemetry.py	91.47%	90.70%	🔴 -0.78%
Total	93.00%	92.99%	⚪️ -0.00%

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