fix: apply missed media/runtime follow-ups from merged PRs

docs/tools/plugin.md

@@ -90,6 +90,22 @@ Notes:
 - Returns PCM audio buffer + sample rate. Plugins must resample/encode for providers.
 - Edge TTS is not supported for telephony.
 
+For STT/transcription, plugins can call:
+
+```ts
+const { text } = await api.runtime.stt.transcribeAudioFile({
+  filePath: "/tmp/inbound-audio.ogg",
+  cfg: api.config,
+  // Optional when MIME cannot be inferred reliably:
+  mime: "audio/ogg",
+});
+```
+
+Notes:
+
+- Uses core media-understanding audio configuration (`tools.media.audio`) and provider fallback order.
+- Returns `{ text: undefined }` when no transcription output is produced (for example skipped/unsupported input).
+
 ## Discovery & precedence
 
 OpenClaw scans, in order: