fix(moq): fail connection on audio codec mismatch in pull node

[staging-devin-ai-integration]

Summary

When catalog discovery during initialize() fails or times out, the MoQ pull node keeps the constructor's default output pin type (Opus). If run_connection() later discovers a different catalog audio codec, it previously only logged a warning but continued sending packets with the mismatched codec — a pin contract violation.

This PR makes run_connection() return Err(StreamKitError::Runtime(...)) on codec mismatch, which causes the reconnection loop (line 197) to retry, giving catalog discovery another chance.

Changes:

• After the existing tracing::warn! in the mismatch block (~line 687), return an error to fail the connection
• Replace the trivial test_codec_mismatch_detectable test (which only asserted Opus != Aac) with four focused tests:
  • test_default_node_has_opus_output_pin — default config produces Opus pin
  • test_codec_mismatch_detected_between_pin_and_catalog — mismatch scenario (Opus pin vs AAC catalog)
  • test_no_mismatch_when_pin_matches_catalog — matching codecs don't trigger failure
  • test_explicit_aac_config_avoids_mismatch_with_aac_catalog — explicit AAC config avoids mismatch

Closes #454

Review & Testing Checklist for Human

• Verify that the error message in run_connection() is clear and actionable in logs
• Confirm that the reconnection loop at line 197 handles this error the same as other StreamKitError::Runtime errors (1s retry)
• Test with a real MoQ broadcast where catalog discovery initially times out but succeeds on retry — verify the node recovers

Notes

This is the safer of the two options from the issue — failing the connection rather than updating pin types at runtime. Runtime pin updates can be done as a follow-up if needed.

Link to Devin session: https://staging.itsdev.in/sessions/8ccfbaefee4d496ab9e2b402efabf989
Requested by: @streamer45

[staging-devin-ai-integration]

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