fix: restore full catalog (stop flash-only wipe)

[SteveSimonson]

Fixes #67

Summary

PR #64 made a healthy flash response the only shop pool. Flash currently publishes ~12 SKUs, so most of the house/BSR assortment disappeared.

This restores flash layered on top of static (dedupe by ASIN). Full collection comes back; live flash still surfaces first.

Risk

Low — reverts assortment policy to pre-wipe merge behavior.

Test plan

• unit tests + lint
• Live /shop product count back to full range after deploy
• Flash items still present when API healthy

[SteveSimonson]

Independent review — fix/restore-static-catalog-merge

Scope: Hotfix for flash-only wipe (#67 / PR #64). Verified merge policy, UI source labels, and contract test.

Verification: merge is flash-over-static (not flash-only)

Confirmed correct. In useFlashCatalog:

function mergeFlashOverStatic(flash: Product[]): Product[] {
  return finalizePool([...flash, ...shopProducts])
}
// ...
if (flashOnly.length > 0) {
  return {
    products: mergeFlashOverStatic(flashOnly),
    flashOnly,
    source: 'merged' as const,
    // ...
  }
}

• Flash products are prepended to shopProducts, then finalizePool dedupes by ASIN (first wins) and slug.
• Result: flash layers on top; full static house/BSR assortment remains.
• Empty/unreachable flash still falls back to finalizePool(shopProducts) with source: 'static'.
• Shop/Home/Product/Quiz/Vibe all consume flash.products, so they all get the restored full pool.

This is the right fix for a ~12-SKU flash control plane wiping the house catalog.

What else looks good

• Shop badge copy updated for merged vs static; shows live flash count without implying emergency-only catalog.
• Contract test updated to assert flash-first ASIN dedupe keeps non-overlapping static SKUs (tests/flash-catalog.test.mjs — passes locally).
• catalog.ts header comment aligned with merge policy.
• Small, focused diff (4 files); low risk revert of assortment policy.

Nits (non-blocking)

1. Dead union member: source: 'flash' | 'static' | 'merged' never returns 'flash' anymore. Drop 'flash' from the type (or keep only if a future path reintroduces flash-only intentionally).
2. No-op error expression:
   error: error || (loading ? undefined : undefined) ≡ error. Simplify for readability.
3. Stale SoT comments outside this diff: src/lib/flashCatalog.ts still says flash is assortment SoT / static is emergency-only. Worth a follow-up so docs match the restored merge policy (catalog.ts filter helper comments still mention “flash SoT” / “static emergency” too).
4. Contract test is a reimplementation, not an import of mergeFlashOverStatic / finalizePool (file already notes Vite/TS import limits). Fine for Phase A, but a future pure export would lock the real function.

Residual risk / test plan

• Unit contract + local test pass; CI lint/build was still pending at review time.
• Post-deploy: confirm /shop product count is full range again and flash SKUs still appear first when the API is healthy.

---

VERDICT: APPROVE_WITH_NITS