fix(query): guard Query.close() cleanup with try/finally (#886)

[MukundaKatta]

Summary

Query.close() runs several await cleanup steps (_transcript_mirror_batcher.close(), child-task cancel, _read_task.wait(), _message_send.close()) before finally calling await self.transport.close(). Because these are not wrapped in try/finally, a raise from any earlier step short-circuits and skips transport.close() — leaking the CLI subprocess and the stderr reader task.

This wraps the pre-transport cleanup in try/finally so transport.close() always runs, regardless of earlier failures.

Fixes #886.

Changes

• src/claude_agent_sdk/_internal/query.py: wrap pre-transport cleanup in try/finally; the await self.transport.close() now lives in the finally branch.
• tests/test_query_close_cleanup.py: regression test that injects a mirror-batcher whose close() raises and asserts transport.close() is still called.

Test plan

• New regression test test_close_runs_transport_close_when_mirror_batcher_close_raises fails on the unpatched code (because transport.close() is never invoked) and passes with the fix.
• Existing close-related tests in tests/test_query.py (test_close_from_same_task_still_works, test_close_from_different_task_does_not_raise, the trio backend variants) still pass — the behavior on the happy path is identical, only the error path changes.
• CI runs the full pytest suite on Ubuntu/macOS/Windows.