fix: accept all document attachments

[zesty-clawd]

Bug Description

Discord/Telegram/Slack would skip non-whitelisted document extensions, so files like .json were treated as empty text-only messages.

Root Cause

Each platform adapter gated document handling on SUPPORTED_DOCUMENT_TYPES and rejected any extension not in the allowlist.

Fix

• Treat any non-media upload as a document instead of skipping it
• Fall back to the attachment MIME type or application/octet-stream for unknown files
• Preserve text injection for common text-like formats, including JSON
• Add regression tests for JSON and unknown-document handling

How to Verify

1. Send a .json file in Discord and confirm it is cached as a document
2. Send a document with no filename/mime in Telegram and confirm it is still cached
3. Run the gateway document tests

Test Plan

• Added regression test for this bug
• Existing tests still pass
• Manual verification of the fix

Risk Assessment

Low — the change only broadens document acceptance and keeps existing media handling unchanged.

[teknium1]

Thanks for the contribution. This is implemented on current main through a broader gateway-wide solution. This is an automated hermes-sweeper review.

• 4314d451ca961cb50c3430197a3a2c7a8575fd0e (fix(gateway): accept any inbound file type across all messaging platforms), shipped in v2026.7.1, changed the shared attachment path.
• gateway/platforms/base.py:1678 now caches every authorized non-media upload as a document instead of rejecting it by extension; unknown files retain their supplied MIME or use application/octet-stream.
• gateway/run.py:10536 surfaces every accepted document to the agent with a path context note.
• tests/gateway/test_document_cache.py:221 covers unknown-file caching and the octet-stream fallback.
• The related discussion in feat: expand supported document types for gateway file uploads #6787 already identifies this broader approach and was closed as implemented by the same commit.