Strut V4 cleanup: provider pruning, preview/UI rewrite, and generation-quality architecture

[amaansyed27]

Goal

Stabilize Strut by stopping unstable provider patching and rewriting the generation/preview path around validated semantic plans, local compilation, and visual QA.

Immediate cleanup already started

• Retire unstable BYOK providers from UI selection.
• Remove dedicated provider-specific router registration.
• Keep BYOK focused on OpenAI, Gemini, and OpenAI-compatible/local endpoint.

Rewrite scope

1. Provider contract

   • Providers return compact semantic plans only.
   • No provider should be trusted to emit full final UI/animation documents directly.
   • Add deterministic local compilation from semantic plan to editable StrutDocument.

2. Visual quality gate

   • Reject outputs with missing requested text marks.
   • Reject tiny/mostly-empty subjects.
   • Reject shadow/blob-only results.
   • Reject timelines without active visible motion.
   • Reject state visibility mistakes where required layers disappear.

3. Preview/runtime

   • Remove white nested-card feel from artboard preview.
   • Make preview state playback obvious and default to a useful animation frame/playback, not a dead edge-view frame.
   • Improve stage scaling, background toggles, and visible subject bounds.

4. UI cleanup

   • Reduce container stacking and visual clutter.
   • Make provider state, generation state, and preview state clear.
   • Hide or disable broken/unsupported provider paths.

5. CLI providers

   • Move CLIs to the same compact-plan contract.
   • Parse/validate locally; do not let CLI prose or pseudo-documents pass.

Non-goals

• No animation-specific hardcoding such as coin/dice/pet special cases.
• No more prompt-only patching as a replacement for architecture changes.