feat(tools): add Voxtral Transcribe STT provider (Mistral AI)

website/docs/user-guide/features/tts.md

@@ -102,11 +102,13 @@ Local transcription works out of the box when `faster-whisper` is installed. If
 ```yaml
 # In ~/.hermes/config.yaml
 stt:
-  provider: "local"           # "local" | "groq" | "openai"
+  provider: "local"           # "local" | "groq" | "openai" | "mistral"
   local:
     model: "base"             # tiny, base, small, medium, large-v3
   openai:
     model: "whisper-1"        # whisper-1, gpt-4o-mini-transcribe, gpt-4o-transcribe
+  mistral:
+    model: "voxtral-mini-latest"  # voxtral-mini-latest, voxtral-mini-2602
 ```
 
 ### Provider Details
@@ -125,6 +127,8 @@ stt:
 
 **OpenAI API** — Accepts `VOICE_TOOLS_OPENAI_KEY` first and falls back to `OPENAI_API_KEY`. Supports `whisper-1`, `gpt-4o-mini-transcribe`, and `gpt-4o-transcribe`.
 
+**Mistral API (Voxtral Transcribe)** — Requires `MISTRAL_API_KEY`. Uses Mistral's [Voxtral Transcribe](https://docs.mistral.ai/capabilities/audio/speech_to_text/) models. Supports 13 languages, speaker diarization, and word-level timestamps. Install with `pip install hermes-agent[mistral]`.
+
 **Custom local CLI fallback** — Set `HERMES_LOCAL_STT_COMMAND` if you want Hermes to call a local transcription command directly. The command template supports `{input_path}`, `{output_dir}`, `{language}`, and `{model}` placeholders.
 
 ### Fallback Behavior
@@ -133,4 +137,5 @@ If your configured provider isn't available, Hermes automatically falls back:
 - **Local faster-whisper unavailable** → Tries a local `whisper` CLI or `HERMES_LOCAL_STT_COMMAND` before cloud providers
 - **Groq key not set** → Falls back to local transcription, then OpenAI
 - **OpenAI key not set** → Falls back to local transcription, then Groq
+- **Mistral key/SDK not set** → Skipped in auto-detect; falls through to next available provider
 - **Nothing available** → Voice messages pass through with an accurate note to the user