chore: checkpoint web Blender feature-gap work, docs and tests

- update native web_engine sources and rebuilt wasm artifacts
- add task cards, status notes and tooling scripts
- add web e2e specs, tutorial UI sources and tutorial assets
- sync golden task manifests and audit records

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

docs/web/deployment-contract.json

@@ -22,7 +22,7 @@
       "Cross-Origin-Opener-Policy": "same-origin",
       "Cross-Origin-Embedder-Policy": "require-corp",
       "Cross-Origin-Resource-Policy": "same-origin",
-      "Content-Security-Policy": "default-src 'self'; script-src 'self' 'wasm-unsafe-eval'; worker-src 'self'; connect-src 'self'; font-src 'self'; img-src 'self' blob:; media-src 'self' blob:; object-src 'none'; base-uri 'none'; frame-ancestors 'none'"
+      "Content-Security-Policy": "default-src 'self'; script-src 'self' 'wasm-unsafe-eval'; style-src 'self'; style-src-attr 'unsafe-inline'; worker-src 'self'; connect-src 'self'; font-src 'self'; img-src 'self' blob:; media-src 'self' blob:; object-src 'none'; base-uri 'none'; frame-ancestors 'none'"
     },
     "routes": [
       {