fix(send_message): deliver Matrix media via adapter

[helix4u]

What does this PR do?

Fixes Matrix media delivery for send_message. The Matrix gateway adapter already supported native file uploads, but tools/send_message_tool.py still treated Matrix like a text-only platform and dropped media attachments before they ever reached the adapter. This wires Matrix into the native adapter-backed media path so generated PDFs and other attachments actually get uploaded to Matrix rooms.

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

• Added a Matrix-specific native media branch in tools/send_message_tool.py so send_message routes Matrix attachments through the Matrix adapter instead of dropping them.
• Added _send_matrix_via_adapter() to preserve native Matrix document/image/audio/video delivery.
• Added targeted tests covering Matrix media routing and adapter-backed document delivery.
• Updated a stale Matrix URL-encoding assertion in tests/tools/test_send_message_missing_platforms.py.

How to Test

1. Configure a Matrix gateway and send a send_message payload that includes a local PDF attachment.
2. Verify the text message still sends and the PDF is uploaded as a Matrix file attachment.
3. Run source venv/bin/activate && python -m pytest tests/tools/test_send_message_tool.py tests/tools/test_send_message_missing_platforms.py -q

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• 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: Ubuntu/WSL

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
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — or N/A
• I've updated tool descriptions/schemas if I changed tool behavior — or N/A

Screenshots / Logs

Targeted test slice passed:

source venv/bin/activate && python -m pytest tests/tools/test_send_message_tool.py tests/tools/test_send_message_missing_platforms.py -q

I also kicked off the full suite, but this workspace was already red outside this change area, so I am not claiming full-suite green here.

[teknium1]

Merged via PR #10602. Your commit was cherry-picked onto current main with authorship preserved in git log. Follow-up fix added: gated the adapter path on media_files presence so text-only Matrix sends continue using the lightweight HTTP helper instead of spinning up a full MatrixAdapter each time. Thanks @helix4u!