feat(skills): add whisper audio transcription skill

Bundled skill that enables the agent to transcribe audio files using
OpenAI Whisper CLI. Uses anyBins requirement so the skill is only
visible when whisper is installed. Includes brew and uv install specs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

skills/whisper/SKILL.md

@@ -0,0 +1,54 @@
+---
+name: Audio Transcription
+description: Transcribe audio files using OpenAI Whisper CLI
+version: 1.0.0
+metadata:
+  emoji: "🎙️"
+  always: true
+  requires:
+    anyBins:
+      - whisper
+      - whisper-cli
+  install:
+    - id: brew-whisper
+      kind: brew
+      formula: openai-whisper
+      bins: [whisper]
+      label: "Install OpenAI Whisper via Homebrew"
+      os: [darwin]
+    - id: pip-whisper
+      kind: uv
+      package: openai-whisper
+      bins: [whisper]
+      label: "Install OpenAI Whisper via pip/uv"
+  tags:
+    - audio
+    - transcription
+    - media
+userInvocable: false
+disableModelInvocation: false
+---
+
+## Audio Transcription
+
+When you receive a message indicating an audio or voice message file (e.g., `[audio message received]` with a `File:` path), you should transcribe it.
+
+### How to Transcribe
+
+Run the following command using the `exec` tool:
+
+```
+whisper "<file_path>" --model turbo --output_format txt --output_dir /tmp
+```
+
+Then read the resulting `.txt` file (same name as input, in `/tmp/`) to get the transcript.
+
+### Response Format
+
+After transcription, respond naturally based on the transcribed content. If the user said something in the voice message, respond to it as if they had typed it.
+
+If transcription fails, let the user know and suggest they check their Whisper installation.
+
+### Supported Formats
+
+Whisper supports: mp3, mp4, mpeg, mpga, m4a, wav, webm, ogg, oga, flac