fix(free-tier): never serve a Radar overlay older than the shipped catalog

[maxmad64bis]

Summary

GET /api/free-tier/summary could still answer from a Radar overlay built 2026-08-02 while this release ships a catalog curated 2026-08-30 (FREE_CATALOG_CURATED_AT). Totals were computed from older data and still tagged catalogSource: radar-overlay. This PR refuses any overlay built before the shipped catalog and, when stale, answers from that catalog through the operator's local state.

Related Issues

• Related to isfree D2 (staleness: overlay vs baseline).
• Tightens fix(free-tier): serve the Radar overlay from /api/free-tier/summary #11550 with the generatedAt persisted by fix(radar): keep the feed's build date in the catalog cache #11435.

Validation

• Change type: provider / routing / UI / i18n / CLI / DB / build-deploy / other
  • actual: other — free-tier route + Radar catalog resolution
• Focused tests and category gates from the golden path
• npm run lint
  • exits 0 on touched files; check:cycles/check:changelog-integrity/prettier --check also green (~500 suppressed pre-existing violations on the base)
• Reconciled with the current active release base; focused checks rerun afterward
  • release/v3.8.51@63e4afa
• Production-code changes include a new or updated automated test in this PR

npx cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --import tsx/esm \
  --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts \
  --test tests/unit/free-tier-summary-radar-overlay.test.ts
# 15/15 pass

Tests Added Or Updated

• tests/unit/free-tier-summary-radar-overlay.test.ts (9 → 15):
  • GEN_AT/FETCHED_AT anchored on FREE_CATALOG_CURATED_AT (+ STALE_GEN_AT); pre-migration (generatedAt: undefined) updated from radar-overlay/null to baseline/FREE_CATALOG_CURATED_AT (still asserts fetchedAt not substituted).
  • 4 freshness: older → baseline, null → baseline, same-day 00:30Z → overlay, newer → overlay.
  • 2 operator-state on stale overlay (naive computeFreeModelTotals({excludeTosAvoid}) fallback fails red, getCatalogWithoutOverlay() passes green):
    not ok 14 — a tombstoned model must never come back … · not ok 15 — a locally disabled model must not be counted …

Coverage Notes

Touches src/app/api/free-tier/summary/route.ts, src/lib/radar/index.ts, src/lib/radar/applyFeed.ts — all covered by the 15 tests above (focused file per plan; full suite + 60% gate run in CI). No touched file loses coverage. Guard is meta.generatedAt.slice(0,10) >= FREE_CATALOG_CURATED_AT (day-level, lexically safe even for +HH:MM); fallback exercises the empty-feed applyFeed path that now honours localOverrides for baseline-only entries.

Reviewer Notes

• Not touched: GET /api/radar/catalog keeps its own contract ("this feed" + its date).
• Guard: overlayIsFresh = meta!==null && meta.generatedAt!==null && slice(0,10) >= FREE_CATALOG_CURATED_AT — unknown is stale, same-day is fresh.
• Fallback: getCatalogWithoutOverlay() = applyFeed({ baseline, feed: [], localOverrides, tombstones }); flag-off path unchanged.
• When stale, isAuthenticated() is short-circuited (read-only, no known side effect).