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

tests/tools/test_tts_kittentts.py

@@ -0,0 +1,198 @@
+"""Tests for the KittenTTS local provider in tools/tts_tool.py."""
+
+import json
+from unittest.mock import MagicMock, patch
+
+import numpy as np
+import pytest
+
+
+@pytest.fixture(autouse=True)
+def clean_env(monkeypatch):
+    for key in ("HERMES_SESSION_PLATFORM",):
+        monkeypatch.delenv(key, raising=False)
+
+
+@pytest.fixture(autouse=True)
+def clear_kittentts_cache():
+    """Reset the module-level model cache between tests."""
+    from tools import tts_tool as _tt
+    _tt._kittentts_model_cache.clear()
+    yield
+    _tt._kittentts_model_cache.clear()
+
+
+@pytest.fixture
+def mock_kittentts_module():
+    """Inject a fake kittentts + soundfile module that return stub objects."""
+    fake_model = MagicMock()
+    # 24kHz float32 PCM at ~2s of silence
+    fake_model.generate.return_value = np.zeros(48000, dtype=np.float32)
+    fake_cls = MagicMock(return_value=fake_model)
+    fake_kittentts = MagicMock()
+    fake_kittentts.KittenTTS = fake_cls
+
+    # Stub soundfile — the real package isn't installed in CI venv, and
+    # _generate_kittentts does `import soundfile as sf` at runtime.
+    fake_sf = MagicMock()
+    def _fake_write(path, audio, samplerate):
+        # Emulate writing a real file so downstream path checks succeed.
+        import pathlib
+        pathlib.Path(path).write_bytes(b"RIFF\x00\x00\x00\x00WAVEfmt fake")
+    fake_sf.write = _fake_write
+
+    with patch.dict(
+        "sys.modules",
+        {"kittentts": fake_kittentts, "soundfile": fake_sf},
+    ):
+        yield fake_model, fake_cls
+
+
+class TestGenerateKittenTts:
+    def test_successful_wav_generation(self, tmp_path, mock_kittentts_module):
+        from tools.tts_tool import _generate_kittentts
+
+        fake_model, fake_cls = mock_kittentts_module
+        output_path = str(tmp_path / "test.wav")
+        result = _generate_kittentts("Hello world", output_path, {})
+
+        assert result == output_path
+        assert (tmp_path / "test.wav").exists()
+        fake_cls.assert_called_once()
+        fake_model.generate.assert_called_once()
+
+    def test_config_passes_voice_speed_cleantext(self, tmp_path, mock_kittentts_module):
+        from tools.tts_tool import _generate_kittentts
+
+        fake_model, _ = mock_kittentts_module
+        config = {
+            "kittentts": {
+                "model": "KittenML/kitten-tts-mini-0.8",
+                "voice": "Luna",
+                "speed": 1.25,
+                "clean_text": False,
+            }
+        }
+        _generate_kittentts("Hi there", str(tmp_path / "out.wav"), config)
+
+        call_kwargs = fake_model.generate.call_args.kwargs
+        assert call_kwargs["voice"] == "Luna"
+        assert call_kwargs["speed"] == 1.25
+        assert call_kwargs["clean_text"] is False
+
+    def test_default_model_and_voice(self, tmp_path, mock_kittentts_module):
+        from tools.tts_tool import (
+            DEFAULT_KITTENTTS_MODEL,
+            DEFAULT_KITTENTTS_VOICE,
+            _generate_kittentts,
+        )
+
+        fake_model, fake_cls = mock_kittentts_module
+        _generate_kittentts("Hi", str(tmp_path / "out.wav"), {})
+
+        fake_cls.assert_called_once_with(DEFAULT_KITTENTTS_MODEL)
+        assert fake_model.generate.call_args.kwargs["voice"] == DEFAULT_KITTENTTS_VOICE
+
+    def test_model_is_cached_across_calls(self, tmp_path, mock_kittentts_module):
+        from tools.tts_tool import _generate_kittentts
+
+        _, fake_cls = mock_kittentts_module
+        _generate_kittentts("One", str(tmp_path / "a.wav"), {})
+        _generate_kittentts("Two", str(tmp_path / "b.wav"), {})
+
+        # Same model name → class instantiated exactly once
+        assert fake_cls.call_count == 1
+
+    def test_different_models_are_cached_separately(self, tmp_path, mock_kittentts_module):
+        from tools.tts_tool import _generate_kittentts
+
+        _, fake_cls = mock_kittentts_module
+        _generate_kittentts(
+            "A", str(tmp_path / "a.wav"),
+            {"kittentts": {"model": "KittenML/kitten-tts-nano-0.8-int8"}},
+        )
+        _generate_kittentts(
+            "B", str(tmp_path / "b.wav"),
+            {"kittentts": {"model": "KittenML/kitten-tts-mini-0.8"}},
+        )
+
+        assert fake_cls.call_count == 2
+
+    def test_non_wav_extension_triggers_ffmpeg_conversion(
+        self, tmp_path, mock_kittentts_module, monkeypatch
+    ):
+        """Non-.wav output path causes WAV → target ffmpeg conversion."""
+        from tools import tts_tool as _tt
+
+        calls = []
+
+        def fake_shutil_which(cmd):
+            return "/usr/bin/ffmpeg" if cmd == "ffmpeg" else None
+
+        def fake_run(cmd, check=False, timeout=None, **kw):
+            calls.append(cmd)
+            # Emulate ffmpeg writing the output file
+            import pathlib
+            out_path = cmd[-1]
+            pathlib.Path(out_path).write_bytes(b"fake-mp3-data")
+            return MagicMock(returncode=0)
+
+        monkeypatch.setattr(_tt.shutil, "which", fake_shutil_which)
+        monkeypatch.setattr(_tt.subprocess, "run", fake_run)
+
+        output_path = str(tmp_path / "test.mp3")
+        result = _tt._generate_kittentts("Hi", output_path, {})
+
+        assert result == output_path
+        assert len(calls) == 1
+        assert calls[0][0] == "/usr/bin/ffmpeg"
+
+    def test_missing_kittentts_raises_import_error(self, tmp_path, monkeypatch):
+        """When kittentts package is not installed, _import_kittentts raises."""
+        import sys
+        monkeypatch.setitem(sys.modules, "kittentts", None)
+        from tools.tts_tool import _generate_kittentts
+
+        with pytest.raises((ImportError, TypeError)):
+            _generate_kittentts("Hi", str(tmp_path / "out.wav"), {})
+
+
+class TestCheckKittenttsAvailable:
+    def test_reports_available_when_package_present(self, monkeypatch):
+        import importlib.util
+        from tools.tts_tool import _check_kittentts_available
+
+        fake_spec = MagicMock()
+        monkeypatch.setattr(
+            importlib.util, "find_spec",
+            lambda name: fake_spec if name == "kittentts" else None,
+        )
+        assert _check_kittentts_available() is True
+
+    def test_reports_unavailable_when_package_missing(self, monkeypatch):
+        import importlib.util
+        from tools.tts_tool import _check_kittentts_available
+
+        monkeypatch.setattr(importlib.util, "find_spec", lambda name: None)
+        assert _check_kittentts_available() is False
+
+
+class TestDispatcherBranch:
+    def test_kittentts_not_installed_returns_helpful_error(self, monkeypatch, tmp_path):
+        """When provider=kittentts but package missing, return JSON error with setup hint."""
+        import sys
+        monkeypatch.setitem(sys.modules, "kittentts", None)
+        monkeypatch.setenv("HERMES_HOME", str(tmp_path))
+
+        from tools.tts_tool import text_to_speech_tool
+
+        # Write a config telling it to use kittentts
+        import yaml
+        (tmp_path / "config.yaml").write_text(
+            yaml.safe_dump({"tts": {"provider": "kittentts"}})
+        )
+
+        result = json.loads(text_to_speech_tool(text="Hello"))
+        assert result["success"] is False
+        assert "kittentts" in result["error"].lower()
+        assert "hermes setup tts" in result["error"].lower()