3D models from the registry: --models-source flag, staging + prod editor builds

The staging editor was built with neither --models-tag (no models on the
staging CDN) nor VITE_MODELS_SOURCE, so modelsSourceConfig() returned null,
no model3d handler was installed and every 3D ensure answered "(unserved)"
despite the chunked packages3D ingest being complete on the staging registry.

- build-editor.mjs: --models-source <cdn|registry> → VITE_MODELS_SOURCE
- deploy-staging.yml: editor builds with --models-source registry
- release.yml: prod editor builds with --models-source registry (libs/0016 §6
  step 4); MODELS_TAG now only feeds the demo build, which has no closed API.

Prod rollout order: split-lib-kinds + packages3D ingest on prod BEFORE the
next release tag — prod's registry currently has 0 model3d libs.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01H1iwtBFvQ8CFg966bqSZh2

.github/workflows/deploy-staging.yml

@@ -97,7 +97,8 @@ jobs:
         run: |
           node scripts/deploy/build-editor.mjs --tag "$STAGING_TAG" \
             --cdn "$CDN_ORIGIN" --api-base "$API_ORIGIN" \
-            --app-base "$APP_ORIGIN" --errors-env staging
+            --app-base "$APP_ORIGIN" --errors-env staging \
+            --models-source registry
           # Worker Static Assets uses not_found_handling=single-page-application.
           # The generated _redirects file is for Pages and duplicates that fallback.
           rm -f web/standalone/dist/_redirects

.github/workflows/release.yml

@@ -188,13 +188,16 @@ jobs:
 
       # --plausible: the shared pa- script covering all pcbjam properties
       # (one dashboard, segment by hostname).
+      # --models-source registry: 3D models come from the closed registry's
+      # kind='model3d' origin libs (chunked packages3D ingest, libs/0016), not
+      # the CDN snapshot — MODELS_TAG only feeds the demo build above.
       - name: Build editor (remote mode)
         run: >
           node scripts/deploy/build-editor.mjs --tag "$RELEASE_TAG"
           --cdn "$CDN" --api-base "$EDITOR_API_BASE" --app-base "$EDITOR_APP_BASE"
           --plausible "https://plausible.io/js/pa-KjNS9YmidydULZTstsjRg.js"
           ${ERRORS_DSN:+--errors-dsn "$ERRORS_DSN" --errors-env production}
-          ${MODELS_TAG:+--models-tag "$MODELS_TAG"}
+          --models-source registry
 
       - name: Ensure Pages project exists
         run: >