feat: add deepgram audio options

docs/nodes/audio.md

@@ -80,6 +80,7 @@ read_when:
 - Provider auth follows the standard model auth order (auth profiles, env vars, `models.providers.*.apiKey`).
 - Deepgram picks up `DEEPGRAM_API_KEY` when `provider: "deepgram"` is used.
 - Deepgram setup details: [Deepgram (audio transcription)](/providers/deepgram).
+- Audio providers can override `baseUrl`/`headers` via `tools.media.audio`.
 - Default size cap is 20MB (`tools.media.audio.maxBytes`). Oversize audio is skipped for that model and the next entry is tried.
 - Default `maxChars` for audio is **unset** (full transcript). Set `tools.media.audio.maxChars` or per-entry `maxChars` to trim output.
 - Use `tools.media.audio.attachments` to process multiple voice notes (`mode: "all"` + `maxAttachments`).

docs/nodes/media-understanding.md

@@ -32,6 +32,8 @@ If understanding fails or is disabled, **the reply flow continues** with the ori
 - `tools.media.models`: shared model list (use `capabilities` to gate).
 - `tools.media.image` / `tools.media.audio` / `tools.media.video`:
   - defaults (`prompt`, `maxChars`, `maxBytes`, `timeoutSeconds`, `language`)
+  - provider overrides (`baseUrl`, `headers`)
+  - Deepgram audio options (`deepgram` in `tools.media.audio`)
   - optional **per‑capability `models` list** (preferred before shared models)
   - `attachments` policy (`mode`, `maxAttachments`, `prefer`)
   - `scope` (optional gating by channel/chatType/session key)