feat: Python telemetry client SDK v0.1.0

Standalone Python package (mosaicstack-telemetry) for reporting
task-completion telemetry and querying predictions from the Mosaic
Stack Telemetry server.

- Sync/async TelemetryClient with context manager support
- Thread-safe EventQueue with bounded deque
- BatchSubmitter with httpx, exponential backoff, Retry-After
- PredictionCache with TTL
- EventBuilder convenience class
- All types standalone (no server dependency)
- 55 tests, 90% coverage, mypy strict clean

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_event_builder.py

@@ -100,12 +100,7 @@ class TestEventBuilder:
     def test_custom_timestamp(self) -> None:
         """Custom timestamp can be set."""
         ts = datetime(2026, 1, 15, 12, 0, 0, tzinfo=timezone.utc)
-        event = (
-            EventBuilder(instance_id=TEST_INSTANCE_ID)
-            .timestamp(ts)
-            .model("test-model")
-            .build()
-        )
+        event = EventBuilder(instance_id=TEST_INSTANCE_ID).timestamp(ts).model("test-model").build()
 
         assert event.timestamp == ts