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>

config/ci/gates.json

@@ -1166,6 +1166,12 @@
       "schemaId": "markdown",
       "production": "source-controlled"
     },
+    {
+      "id": "artifact-artifacts-tests-a11y-manual-TECH-LOG-STUDIO-ASSETS-md",
+      "path": "artifacts/tests/a11y-manual/TECH_LOG_STUDIO_ASSETS.md",
+      "schemaId": "markdown",
+      "production": "source-controlled"
+    },
     {
       "id": "artifact-artifacts-tests-a11y-manual-TECH-LOG-STUDIO-NOT-FOUND-md",
       "path": "artifacts/tests/a11y-manual/TECH_LOG_STUDIO_NOT_FOUND.md",
@@ -1916,6 +1922,7 @@
         "artifact-artifacts-tests-a11y-manual-TECH-LOG-STUDIO-DOCUMENT-PUBLISH-md",
         "artifact-artifacts-tests-a11y-manual-TECH-LOG-STUDIO-PUBLICATIONS-md",
         "artifact-artifacts-tests-a11y-manual-TECH-LOG-STUDIO-PUBLICATION-PREVIEW-md",
+        "artifact-artifacts-tests-a11y-manual-TECH-LOG-STUDIO-ASSETS-md",
         "artifact-artifacts-tests-a11y-manual-TECH-LOG-STUDIO-NOT-FOUND-md",
         "artifact-artifacts-tests-a11y-manual-NOT-FOUND-md",
         "artifact-artifacts-tests-a11y-manual-report-json"