# SHiRE Academy Stage 3B.3 — Fast 3D Viewer and Direct Downloads

Optimises the existing local WebGL STL viewer and puts the real draft downloads directly inside the 3D inspection screen.

## What changes

- Adds **Download STL** and **Download STEP** inside the 3D viewer.
- Clarifies that the model being inspected is already the exact real `object_draft.stl` from the completed Fast Builder job.
- Replaces the old permanent 60 FPS redraw loop with render-on-demand. The viewer redraws only after rotation, pan, zoom, resize or a control change; continuous frames run only when auto-rotate is enabled.
- Parses binary STL directly into typed arrays instead of constructing a large per-triangle JavaScript object graph.
- Builds wireframe edge data only when wireframe is actually enabled.
- Defaults to a speed-focused pixel ratio; high-resolution mode is optional.
- Allows immutable browser caching for completed STL/STEP job artifacts, improving repeat opens through the Tailscale SSH tunnel.
- Shows measured viewer readiness time.

## Safety boundaries preserved

- Academy remains localhost-only through the existing SSH/Tailscale tunnel.
- Only the existing allowlisted `object_draft.stl` and corresponding `object_draft.step` job artifacts are offered.
- The 371-skill Academy state remains read-only.
- No counted attempt, certification or Forge permission changes.
- No production approval and no replacement for slicer inspection.
- No npm, CDN, external runtime or public port.

Target version: `0.8.2-stage3b.3-fast-3d-viewer-downloads`.