fix(gateway): transcribe configured Discord audio attachments

[mgreez]

What does this PR do?

Related Issue

Fixes #

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

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Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
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• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform:

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
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Screenshots / Logs

[teknium1]

Thanks for preserving the default file-attachment behavior and making the proposed STT route channel-scoped.

Problems

• The changed MessageType.AUDIO branch still routes every path in event.media_urls to STT. Current main has per-attachment MIME classification in gateway/run.py:2024-2029; a mixed Discord message whose first attachment is audio can also contain image/document paths, and those must not be transcribed. See tests/gateway/test_mixed_attachment_routing.py:55-59.
• tests/gateway/test_discord_audio_attachment_stt.py tests the predicate but not the live _prepare_inbound_message_text → transcribe_audio path, so the configured and unconfigured end-to-end behaviors are not covered.
• The configuration bridge has moved to gateway/config.py:1156-1235, and the Discord adapter is now under plugins/platforms/discord/adapter.py; this needs a current-main salvage. Please also document the new user-facing setting near website/docs/user-guide/messaging/discord.md:310-335.

Suggested changes

• Use _event_media_is_audio(event, i) for the opt-in routing and add mixed-media regression coverage.
• Add configured/unconfigured inbound-pipeline tests with mocked transcribe_audio.

Automated hermes-sweeper review.

[teknium1]

Please classify each attachment before appending it here. An AUDIO-typed Discord message can contain mixed media; routing every event.media_urls entry through STT would send accompanying images/documents to transcribe_audio. Current main provides _event_media_is_audio(event, i) for this per-MIME distinction.

[andrexibiza]

Vox Lockin lane 07 probe — feature absent on main, PR stale/conflicting; not part of the delivery-reliability class.

Probe against origin/main @ 70db671fac:

• The feature is absent on main: gateway/run.py classifies MessageType.AUDIO as "never STT" (_event_media_is_stt_input returns False for AUDIO/DOCUMENT; _prepare_inbound_message_text routes audio attachments to audio_file_paths), and there is no transcribe_audio_attachment_channels config anywhere.
• This PR's head (5063277187) is stale (merge base 7a4dc8e8d6) and CONFLICTING against main (gateway/run.py moved substantially since).
• It is an opt-in feature (transcribe configured Discord audio attachments) rather than a delivery-reliability bug, so it sits outside the lane-07 corpus (BUG: TTS/MEDIA voice messages never delivered via gateway (false-positive history dedup) #74928/fix(gateway): bound voice transcription stalls #74051/fix(gateway): handle silent audio and media producers #65745) and I did not ship it in fix(gateway): serialize STT/TTS reliability slice behind V6 contract #78196.

Recommendation: rebase and re-open for review as a feature; the diff is clean and the tests (test_discord_audio_attachment_stt.py) look solid. No duplicate PR opened.