phase: 91_admin_theme_tab

All verification is complete — this pass needed no code changes. Final report:

**Phase 91 — Admin Theme tab: final verification pass (all 6 tasks already in `complete/`)**

- Verified pre-paint theming end-to-end: `ui_settings` store + resolver, admin `GET/PUT /api/ui-settings`, `CachingMiddleware` inline-`<style id="bor-theme">` injection before `</head>` (incl. `/shared/<token>` prefix branch, unit-pinned), CSP sha256 exemption for the inline tag, Theme tab shell + `theme.js` editor, CSS-file theming fully retired.
- No defects found; zero changes made — working tree left exactly as the task executors left it.
- Tests: `uv run pytest --cov=app` → 1841 passed, 0 failed (TOTAL coverage **99%**; theming/ui_settings/caching all 100%); `uv run pytest tests/e2e/test_admin_theme_tab.py -v --no-cov` → **5 passed** in isolation.
- Lint/types: `uv run ruff check .` → All checks passed; `uv run pyright` → 0 errors, 0 warnings.
- Criteria: (1) unset deployment byte-identical, no `#bor-theme` anywhere — ✓ (unit no-op test + E2E reset byte-compare); `rg "BOR_THEME|themes/"` → single hit is the permitted doc-history comment in `frontend/index.html`. (2) admin-only gate + 403s for anonymous and token users — ✓ (E2E test 3). (3) saved theme inline before `</head>` on every page incl. `/shared/<token>`, computed `--brand` on first paint for admin + anonymous — ✓ (E2E test 2 + unit). (4) reset → byte-identical; 5 contrast pairs warn <4.5:1, non-blocking — ✓ (E2E tests 4–5). (5) suite green, >90% coverage, lint clean — ✓. (6) commit deferred to harness per rules.
- Notable: `.agents/PLAN.md` is absent from the repo — the phase overview's Design section was used as the binding spec; no deviation resulted.
- Next pending phase: **none** — 91 is the last phase in `todo/`.

frontend/shared.html

@@ -59,6 +59,13 @@
              page — test_nav_consistency pins the inventory parity).
              Null-safe: header.js is a no-op on a page without it. -->
         <a href="/tokens.html" class="nav-link" id="nav-tokens" hidden>Tokens</a>
+        <!-- Phase 91 (task 04): the Theme link is admin-only — hidden
+             by default, header.js reveals it once whoami says admin,
+             exactly like the Tokens link above (the phase-34 one-bar
+             contract: the SAME nav ships on every page —
+             test_nav_consistency pins the inventory parity).
+             Null-safe: header.js is a no-op on a page without it. -->
+        <a href="/theme.html" class="nav-link" id="nav-theme" hidden>Theme</a>
         <!-- Phase 46 (mobile dropdown copy: sign-in — desktop bar copy is
              outside the nav; see styles.css .sign-in-mobile rules). -->
         <a href="/login.html?next=/" class="auth-link sign-in-link sign-in-mobile" id="sign-in-link-mobile" hidden>