feat(tts): complete KittenTTS integration (tools/setup/docs/tests)

Builds on @AxDSan's PR #2109 to finish the KittenTTS wiring so the
provider behaves like every other TTS backend end to end.

- tools/tts_tool.py: `_check_kittentts_available()` helper and wire
  into `check_tts_requirements()`; extend Opus-conversion list to
  include kittentts (WAV → Opus for Telegram voice bubbles); point the
  missing-package error at `hermes setup tts`.
- hermes_cli/tools_config.py: add KittenTTS entry to the "Text-to-Speech"
  toolset picker, with a `kittentts` post_setup hook that auto-installs
  the wheel + soundfile via pip.
- hermes_cli/setup.py: `_install_kittentts_deps()`, new choice + install
  flow in `_setup_tts_provider()`, provider_labels entry, and status row
  in the `hermes setup` summary.
- website/docs/user-guide/features/tts.md: add KittenTTS to the provider
  table, config example, ffmpeg note, and the zero-config voice-bubble tip.
- tests/tools/test_tts_kittentts.py: 10 unit tests covering generation,
  model caching, config passthrough, ffmpeg conversion, availability
  detection, and the missing-package dispatcher branch.

E2E verified against the real `kittentts` wheel:
- WAV direct output (pcm_s16le, 24kHz mono)
- MP3 conversion via ffmpeg (from WAV)
- Telegram flow (provider in Opus-conversion list) produces
  `codec_name=opus`, 48kHz mono, `voice_compatible=True`, and the
  `[[audio_as_voice]]` marker
- check_tts_requirements() returns True when kittentts is installed

tools/tts_tool.py

@@ -703,6 +703,15 @@ def _check_neutts_available() -> bool:
         return False
 
 
+def _check_kittentts_available() -> bool:
+    """Check if the kittentts engine is importable (installed locally)."""
+    try:
+        import importlib.util
+        return importlib.util.find_spec("kittentts") is not None
+    except Exception:
+        return False
+
+
 def _default_neutts_ref_audio() -> str:
     """Return path to the bundled default voice reference audio."""
     return str(Path(__file__).parent / "neutts_samples" / "jo.wav")
@@ -955,7 +964,8 @@ def text_to_speech_tool(
                 return json.dumps({
                     "success": False,
                     "error": "KittenTTS provider selected but 'kittentts' package not installed. "
-                             "Run: pip install https://github.com/KittenML/KittenTTS/releases/download/0.8.1/kittentts-0.8.1-py3-none-any.whl"
+                             "Run 'hermes setup tts' and choose KittenTTS, or install manually: "
+                             "pip install https://github.com/KittenML/KittenTTS/releases/download/0.8.1/kittentts-0.8.1-py3-none-any.whl"
                 }, ensure_ascii=False)
             logger.info("Generating speech with KittenTTS (local, ~25MB)...")
             _generate_kittentts(text, file_str, tts_config)
@@ -1084,6 +1094,8 @@ def check_tts_requirements() -> bool:
         pass
     if _check_neutts_available():
         return True
+    if _check_kittentts_available():
+        return True
     return False