feat(parse): support AC-3 audio resources and add multimodal integration tests

[Hao-Yu-la]

Description

Add AC-3 audio resource support and introduce a black-box multimodal compatibility test matrix against a deployed OpenViking
service.

The integration tests submit remote file URLs directly through AsyncHTTPClient without mocking parsers, storage, or media
validation.

Human Involvement

• A human participated in the implementation or review loop
• This PR was generated entirely by AI agents without human participation in the loop

Related Issue

N/A

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test update

Changes Made

• Added URL detection coverage to ensure remote AC-3 resources retain the .ac3 extension and route to the audio parser.
• Added a 31-case multimodal integration matrix covering image, audio, video, codec, and document inputs through a real
  deployed OpenViking service.
• Added support for loading the service URL, API key, and identity fields from the current OV CLI configuration, with
  localhost fallback when no URL is configured.
• Removed the separate AC-3 parser test in favor of the consolidated multimodal compatibility matrix.

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have tested this on the following platforms:
  • Linux
  • macOS
  • Windows

Commands executed:

uv run --active --no-sync pytest -q \
  tests/parse/test_url_filename_preservation.py \
  tests/parse/test_multimodal_file_matrix_integration.py \
  --no-cov

Result:

49 passed, 31 skipped

The complete live matrix was also validated against a deployed OpenViking service with valid credentials:

38 passed

Style validation:

 uv run --active --no-sync ruff check \
    tests/parse/test_multimodal_file_matrix_integration.py

Result:

All checks passed!

Checklist

• My code follows the project's coding style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Screenshots (if applicable)

N/A

Additional Notes

• Live integration cases are opt-in through OPENVIKING_RUN_MULTIMODAL_INTEGRATION=1.

• The tests use add_resource(wait=False) to validate file-format acceptance and resource creation without waiting for
  downstream semantic extraction or embedding queues.

• A later live rerun was blocked by an invalid API key in the active local CLI configuration; this occurred before resource
  ingestion and is unrelated to format handling.

• No external dependency changes are required.