fix(gateway): unify extract_media + extract_local_files extension lists (#34321)

[Bartok9]

Closes #34321

Problem

BasePlatformAdapter.extract_media() rejects .md (and 22 other text-based extensions) that extract_local_files() correctly accepts. MEDIA: tags pointing to those files fall through to plain text on every platform, while a bare path in the same response delivers as a native attachment.

Commit ea49b3862 narrowed the extract_media regex to fix Mattermost false positives, but left out:

.md .doc .odt .rtf .ods .tsv .json .xml .yaml .yml .ppt .odp
.key .tar .gz .tgz .bz2 .xz .html .htm .tiff .svg .bmp

Reproduction (from issue)

send_message(message='MEDIA:~/.hermes/cache/documents/report.md',
             target='weixin')

• Before: literal MEDIA:~/.hermes/... delivered as text
• After: report.md uploaded as native attachment ✅

Fix

Extract the extension list into a class-level constant BasePlatformAdapter._MEDIA_DELIVERY_EXTS and use it in both extract_media() and extract_local_files(). Single source of truth eliminates the drift class.

Implementation notes:

• _MEDIA_DELIVERY_EXTS is a class attribute (Tuple[str, ...]) so subclass overrides work naturally if a platform ever needs to narrow it.
• Regex alternation sorted by length descending so .tgz wins against .gz (would short-circuit otherwise).
• Added re.IGNORECASE on extract_media to match the case-insensitivity already in extract_local_files. Real responses include MEDIA:/path/foo.PDF.
• Union of both prior lists: .epub/.opus/.apk/.ipa were in extract_media but missing from extract_local_files. Both sets now in the shared constant.

Tests

10 new tests in TestExtractMediaExtensionParity:

• Shared constant exists, non-empty, contains .md
• Parametrized across all 23 previously-missing extensions: each is in the constant AND matches via extract_media()
• Real-world extract_media() regex missing .md and other text-based extensions, mismatch with extract_local_files() #34321 reproduction case (MEDIA:~/.hermes/cache/documents/report.md)
• Cross-method probe: both methods accept the same set on real files at /tmp
• [[audio_as_voice]] still applies to .md (behavior preserved)
• Unknown extensions like .exe still rejected (this fix expands the allow-list, doesn't open the gate)

$ python -m pytest tests/gateway/test_platform_base.py tests/gateway/test_extract_local_files.py tests/gateway/test_media_extraction.py
=== 209 passed, 2 skipped in 1.58s ===

Files changed

File	Change
gateway/platforms/base.py	+49 / -19 (shared constant + both methods use it)
tests/gateway/test_platform_base.py	+99 / 0 (10 new tests)

🎻 Co-authored-by: Cursor cursoragent@cursor.com

[alt-glitch]

Part of the saturated MEDIA extension list cluster: #29609 (dynamic derivation, preferred), #31138, #31150 (closed), #22492, #30588. Fixes #34321.

[teknium1]

Merged via #34844, which consolidates the MEDIA: extension-allowlist cluster.

Your contribution was used directly and your authorship is preserved via a Co-authored-by: trailer on the merge commit (781604c on main). #34844 fixes both halves of issue #34517: it unifies extract_media and extract_local_files onto one shared extension set AND gates the cleanup strip so unknown-extension paths are no longer silently dropped.

Thanks for the work here.