fix(gateway): add missing send_voice() override to WhatsApp adapter

[luyao618]

What does this PR do?

Adds the missing send_voice() method to the WhatsApp platform adapter. WhatsApp was the only adapter without this override — voice/audio messages fell back to the base class implementation which sent them as plain text paths (e.g. 🔊 Audio: /path/to/file.mp3) instead of native media attachments.

Related Issue

Fixes #9236

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)

Changes Made

Added send_voice() to gateway/platforms/whatsapp.py that routes through the existing _send_media_to_bridge() with media_type="audio", consistent with send_image, send_video, and send_document.

The WhatsApp bridge (bridge.js) already handles the "audio" media type — it reads the file and sends sock.sendMessage({ audio: buffer, mimetype: "audio/mpeg" }). No bridge-side changes needed.

How to Test

1. Configure Hermes with a WhatsApp gateway
2. Trigger a voice message (e.g., TTS tool output or voice reply)
3. Before: User receives plain text like 🔊 Audio: /tmp/hermes_voice/tts_reply_abc123.mp3
4. After: User receives a native audio attachment in WhatsApp

Run the test suite:

pytest tests/gateway/test_whatsapp_send_voice.py -v

Tests verify:

• send_voice method exists and is not the base class fallback ✅
• Method signature matches the base class interface ✅
• Routes through _send_media_to_bridge with type "audio" ✅
• All media methods (image, video, document, voice) are overridden ✅

Full suite:

pytest tests/ -q --ignore=tests/integration --ignore=tests/e2e

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes
• I've tested on my platform: macOS (Darwin 25.4.0, Apple Silicon), Python 3.11

Documentation & Housekeeping

• Updated relevant documentation — or N/A
• Updated cli-config.yaml.example — or N/A
• Updated CONTRIBUTING.md or AGENTS.md — or N/A
• Considered cross-platform impact — or N/A
• Updated tool descriptions/schemas — or N/A

[teknium1]

Thanks for the contribution, @luyao618!

Closing this as a duplicate of #6305 (by @duan78), which targets the same fix/feature. We're consolidating on that PR for review.

If you want to help push it over the line, please jump in there — or if you think your approach is better for a specific reason that isn't covered in the other PR, let us know and we can reopen.