Add pipeline studio web UI (demucs -> AuK -> MOSS-TTS)

Gradio app that orchestrates the three existing isolated venvs via
subprocess (their dependencies conflict too much to merge into one
environment - MOSS-TTS needs transformers 5.0.0, AuK needs 4.57.6).

Lets you strip a voice, iteratively edit it (emotion/pitch/speed/custom
instruction) with preview and undo/reset after each step, then generate
new speech in the resulting voice - addressing the trial-and-error
workflow the pitch-overshoot investigation needed.

Also extracts tts/generate.py as a reusable, general-purpose MOSS-TTS
cloning CLI (text/reference/language/output args) rather than one-off
personal scripts.

Verified all three stages end to end via direct function calls before
wiring up the UI.

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Y1oQ4h4WE4R9KRvMQLr5Ey

README.md

@@ -9,6 +9,7 @@ Audio processing demos: WhisperX, Demucs, and TTS technology proofs-of-concept.
 - `tts/` — text-to-speech service demos (voice cloning via MOSS-TTS)
 - `auk/` — voice *editing* demos (emotion/pitch/speed/content editing on existing recordings,
   as opposed to `tts/`'s clone-and-generate approach)
+- `webui/` — interactive pipeline studio chaining demucs -> AuK -> MOSS-TTS with previews
 
 Each subdirectory has its own README with setup and run instructions.