feat(live): filter internal _adk_live artifact parts from live session history - #7346

…n history

When `RunConfig.save_live_blob=True` is enabled, live sessions persist realtime
audio, image, and video blobs to `BaseArtifactService` and record internal
`artifact://.../_adk_live/...` `FileData` references (including single-frame
media files and multi-frame `application/zip` archives) on session events.
Those internal `artifact://` URIs cannot be resolved by the Gemini Live API's
`send_client_content` endpoint when session history is replayed on reconnect or
agent transfer.

This change adds `is_adk_live_artifact_part()` in `utils/content_utils.py` and
updates `filter_audio_parts()` (used by `GeminiLlmConnection.send_history()`)
to strip internal `_adk_live` artifact `FileData` parts while preserving text,
inline media blobs, and external `gs://` / `https://` `FileData` parts.

Testing Plan:
- Added unit tests in `tests/unittests/utils/test_content_utils.py` covering
  `is_adk_live_artifact_part()` (multi-frame `.zip`, single-frame `.jpeg`,
  parameterized/uppercase MIME strings, `None` fields, external `gs://` URIs,
  and inline blobs) and `filter_audio_parts()`.
- Added `test_send_history_filters_out_adk_live_artifact_parts` in
  `tests/unittests/models/test_gemini_llm_connection.py`.

PiperOrigin-RevId: 990462563