docs: audit mdx docs against multi-engine backend (#484)

* docs: audit mdx docs against multi-engine backend and refresh stale content

Rewrote developer-facing docs that predated the TTSBackend Protocol /
ModelConfig registry refactor (architecture, tts-generation,
model-management, transcription). Updated user-facing docs to reflect all
seven shipped engines (Qwen, Qwen CustomVoice, LuxTTS, Chatterbox,
Chatterbox Turbo, TADA, Kokoro) instead of the outdated "5 engines" claim.

Also fixes:
- Stale app identifier (com.voicebox.app → sh.voicebox.app)
- CUDA backend update flow (now two-archive split, not N-way chunks)
- Whisper model list (removed tiny, added turbo)
- Broken /development/ and /guides/ route links
- Stale just commands and install steps (missing --no-deps chatterbox/tada)
- Removed ASCII art diagrams from README and stories.mdx
- History Generation schema sync with DB model

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

* docs: add DeepWiki badge to README

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

* docs: address PR review feedback

- architecture.mdx: fix backends/ file list (remove nonexistent qwen_backend.py, rename tada_backend.py → hume_backend.py)
- model-management.mdx: Kokoro language count 9 → 8 (matches ModelConfig)
- model-management.mdx: ProgressManager path services/ → utils/
- tts-generation.mdx: ModelConfig example uses field(default_factory=...) — mutable default would raise at runtime
- tts-generation.mdx: "1080p samples" → "on CUDA" (1080p is video, not audio)
- PROJECT_STATUS.md: replace ASCII architecture diagram with prose (matches no-ASCII-art rule)

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

* fix(app): guard against undefined engine in FloatingGenerateBox preset check

form.getValues('engine') returns string | undefined; Set<string>.has()
rejects undefined under strict mode. Added a truthy guard before the
preset lookup.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <[email protected]>

docs/content/docs/overview/introduction.mdx

@@ -5,13 +5,14 @@ description: "Voicebox is a local-first voice cloning studio -- a free and open-
 
 ## What is Voicebox?
 
-Voicebox is a **local-first voice cloning studio** -- a free and open-source alternative to ElevenLabs. Clone voices from a few seconds of audio, generate speech in 23 languages across 5 TTS engines, apply post-processing effects, and compose multi-voice projects with a timeline editor.
+Voicebox is a **local-first voice cloning studio** -- a free and open-source alternative to ElevenLabs. Clone voices from a few seconds of audio or pick from 50+ preset voices, generate speech in 23 languages across 7 TTS engines, apply post-processing effects, and compose multi-voice projects with a timeline editor.
 
 - **Complete privacy** -- models and voice data stay on your machine
-- **5 TTS engines** -- Qwen3-TTS, LuxTTS, Chatterbox Multilingual, Chatterbox Turbo, and HumeAI TADA
+- **7 TTS engines** -- Qwen3-TTS, Qwen CustomVoice, LuxTTS, Chatterbox Multilingual, Chatterbox Turbo, HumeAI TADA, and Kokoro
+- **Cloning and preset voices** -- zero-shot cloning from a reference sample, or curated preset voices via Kokoro (50 voices) and Qwen CustomVoice (9 voices)
 - **23 languages** -- from English to Arabic, Japanese, Hindi, Swahili, and more
 - **Post-processing effects** -- pitch shift, reverb, delay, chorus, compression, and filters
-- **Expressive speech** -- paralinguistic tags like `[laugh]`, `[sigh]`, `[gasp]` via Chatterbox Turbo
+- **Expressive speech** -- paralinguistic tags like `[laugh]`, `[sigh]`, `[gasp]` via Chatterbox Turbo; natural-language delivery control via Qwen CustomVoice
 - **Unlimited length** -- auto-chunking with crossfade for scripts, articles, and chapters
 - **Stories editor** -- multi-track timeline for conversations, podcasts, and narratives
 - **API-first** -- REST API for integrating voice synthesis into your own projects
@@ -20,15 +21,17 @@ Voicebox is a **local-first voice cloning studio** -- a free and open-source alt
 
 ## TTS Engines
 
-Five engines with different strengths, switchable per-generation:
+Seven engines with different strengths, switchable per-generation:
 
-| Engine | Languages | Strengths |
-|--------|-----------|-----------|
-| **Qwen3-TTS** (0.6B / 1.7B) | 10 | High-quality multilingual cloning, delivery instructions |
-| **LuxTTS** | English | Lightweight (~1GB VRAM), 48kHz output, 150x realtime on CPU |
-| **Chatterbox Multilingual** | 23 | Broadest language coverage |
-| **Chatterbox Turbo** | English | Fast 350M model with paralinguistic emotion/sound tags |
-| **TADA** (1B / 3B) | 10 | HumeAI speech-language model -- 700s+ coherent audio |
+| Engine | Profile Type | Languages | Strengths |
+|--------|--------------|-----------|-----------|
+| **Qwen3-TTS** (0.6B / 1.7B) | Cloned | 10 | High-quality multilingual cloning |
+| **Qwen CustomVoice** (0.6B / 1.7B) | Preset (9 voices) | 10 | Natural-language delivery control (tone, emotion, pace) |
+| **LuxTTS** | Cloned | English | Lightweight (~1GB VRAM), 48kHz output, 150x realtime on CPU |
+| **Chatterbox Multilingual** | Cloned | 23 | Broadest language coverage |
+| **Chatterbox Turbo** | Cloned | English | Fast 350M model with paralinguistic emotion/sound tags |
+| **TADA** (1B / 3B) | Cloned | 10 | HumeAI speech-language model -- 700s+ coherent audio |
+| **Kokoro** | Preset (50 voices) | 9 | 82M parameters, CPU realtime, lowest VRAM of any engine |
 
 ## GPU Support
 
@@ -57,7 +60,7 @@ Five engines with different strengths, switchable per-generation:
 | Frontend | React, TypeScript, Tailwind CSS |
 | State | Zustand, React Query |
 | Backend | FastAPI (Python) |
-| TTS Engines | Qwen3-TTS, LuxTTS, Chatterbox, Chatterbox Turbo, TADA |
+| TTS Engines | Qwen3-TTS, Qwen CustomVoice, LuxTTS, Chatterbox, Chatterbox Turbo, TADA, Kokoro |
 | Effects | Pedalboard (Spotify) |
 | Transcription | Whisper / Whisper Turbo (PyTorch or MLX) |
 | Inference | MLX (Apple Silicon) / PyTorch (CUDA/ROCm/XPU/CPU) |