chore: cleanup #6 #8 #9 — delete debug dir, rename glbUrl prop, sync docs

- delete renderproblems_tmp/ (7 debug images + USD test files, orphaned)
- rename ThreeDViewer prop geometryGltfUrl → glbUrl; update CadPreview.tsx
  caller (productionGltfUrl distinction was never needed, only one GLB type)
- plan.md: mark all 4 cinematic tasks [x] (all implemented + seeded in 070)
- 0001-step-to-usd: mark Phase 4 ThreeDViewer acceptance gates [x] (P4 done)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/cad/ThreeDViewer.tsx

@@ -55,7 +55,7 @@ export interface ThreeDViewerProps {
   cadFileId: string
   onClose: () => void
   /** URL for the geometry-only GLB (from OCC export) */
-  geometryGltfUrl?: string
+  glbUrl?: string
   hasGeometryGlb?: boolean
   onGenerateGeometry?: () => void
   isGeneratingGeometry?: boolean
@@ -366,7 +366,7 @@ function TBtn({ active, onClick, title, children, disabled }: {
 export default function ThreeDViewer({
   cadFileId,
   onClose,
-  geometryGltfUrl,
+  glbUrl,
   hasGeometryGlb,
   onGenerateGeometry,
   isGeneratingGeometry,
@@ -501,7 +501,7 @@ export default function ThreeDViewer({
   )
 
   // Raw URL (used as stable key before blob fetch)
-  const rawActiveUrl = geometryGltfUrl
+  const rawActiveUrl = glbUrl
 
   // Resolved blob URL used in useGLTF (requires auth header)
   const activeUrl = blobUrl

frontend/src/pages/CadPreview.tsx

@@ -119,7 +119,7 @@ export default function CadPreviewPage() {
     <ThreeDViewer
       cadFileId={id}
       onClose={() => navigate(-1)}
-      geometryGltfUrl={latestGltf?.download_url ?? undefined}
+      glbUrl={latestGltf?.download_url ?? undefined}
       hasGeometryGlb={!!latestGltf}
       isGeneratingGeometry={generating}
       onGenerateGeometry={() => generateMutation.mutate()}