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>

artifacts/tests/a11y-manual/TECH_LOG_STUDIO_ASSETS.md

@@ -0,0 +1,18 @@
+# TECH_LOG_STUDIO_ASSETS accessibility review
+
+Status: pending-manual-review
+Route ID: TECH_LOG_STUDIO_ASSETS
+Release ID:
+Reviewer:
+Reviewed at:
+Signature:
+Attestation: pending
+M1 Keyboard: pending
+M2 Visible focus: pending
+M3 Route focus: pending
+M4 Modal focus: pending
+M5 Error association: pending
+M6 Color signal: pending
+M7 Reduced motion: pending
+Screen reader: pending
+Notes: Human review pending; automated evidence does not replace signed keyboard, focus, and screen-reader review.