feat(tts): add Gemini persona prompt file

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

@@ -68,6 +68,7 @@ tts:
   gemini:
     model: "gemini-2.5-flash-preview-tts"  # or gemini-2.5-pro-preview-tts
     voice: "Kore"               # 30 prebuilt voices: Zephyr, Puck, Kore, Enceladus, Gacrux, etc.
+    persona_prompt_file: ""      # Optional Markdown/text file with Gemini voice direction
   xai:
     voice_id: "eve"             # or a custom voice ID — see docs below
     language: "en"              # ISO 639-1 code
@@ -97,6 +98,20 @@ tts:
 
 **Speed control**: The global `tts.speed` value applies to all providers by default. Each provider can override it with its own `speed` setting (e.g., `tts.openai.speed: 1.5`). Provider-specific speed takes precedence over the global value. Default is `1.0` (normal speed).
 
+### Gemini Persona Prompts
+
+Gemini TTS can follow natural-language performance direction. Set `tts.gemini.persona_prompt_file` to a local Markdown or text file that describes the voice persona. The file can include Gemini-style sections such as `AUDIO PROFILE`, `SCENE`, `DIRECTOR'S NOTES`, `SAMPLE CONTEXT`, and `TRANSCRIPT`.
+
+If the file contains `{transcript}` or `{{ transcript }}`, Hermes replaces that placeholder with the live TTS text. Otherwise, Hermes appends a labeled `TRANSCRIPT` section automatically. The persona prompt stays local and is not shown in the chat reply.
+
+```yaml
+tts:
+  provider: gemini
+  gemini:
+    voice: Algieba
+    persona_prompt_file: ~/.hermes/tts/butler-voice.md
+```
+
 
 ### Input length limits
 
@@ -109,7 +124,7 @@ Each provider has a documented per-request input-character cap. Hermes truncates
 | xAI | 15000 |
 | MiniMax | 10000 |
 | Mistral | 4000 |
-| Google Gemini | 5000 |
+| Google Gemini | 32000 |
 | ElevenLabs | Model-aware (see below) |
 | NeuTTS | 2000 |
 | KittenTTS | 2000 |