feat: add the TechLog Studio asset library route and screen

Adds TECH_LOG_STUDIO_ASSETS (/studio/assets) as a route reachable but
excluded from primary Studio navigation (navigationLabel/navigationOrder
null), plus the AssetLibrary screen that lists assets, shows usage, and
lets an operator archive or hard-delete one. canHardDelete() is a pure
gate mirroring the server's ASSET_IN_USE rule so the screen never offers
an action the server would refuse.

Adding a 28th route also required updating the route-scoped CI
accessibility-evidence gate (FE-GATE-009 in config/ci/gates.json, plus
its authority-baseline counts and shape digest in
scripts/contracts/ci-gates.ts) and the Vite route-to-chunk map that
scripts/generate-build-manifest.ts depends on, or test:unit and the
production build both fail. See task-11-report.md for the full
breakdown.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

vite.config.ts

@@ -30,6 +30,7 @@ const techLogRouteChunks = Object.freeze({
   "/studio/pages/document-publish-page.tsx": "route-tech-log-studio-document-publish",
   "/studio/pages/publications-page.tsx": "route-tech-log-studio-publications",
   "/studio/pages/publication-preview-page.tsx": "route-tech-log-studio-publication-preview",
+  "/studio/pages/assets-page.tsx": "route-tech-log-studio-assets",
   "/studio/pages/studio-not-found-page.tsx": "route-tech-log-studio-not-found",
   "/public/pages/public-not-found-page.tsx": "route-not-found",
 } as const);