fix(providers): empty refresh must not resurface just-cleared synced models

[diegosouzapw]

Why

The combined release-branch validation (typecheck + full test:unit) surfaced one real pre-existing failure:

✖ provider models route clears cached discovery when a refresh returns no remote models
  assert.ok(body.models.every((model) => model.id !== "cached-go"))  // false

Root cause — interaction of two prior merges: #3148 (synced models become the authoritative local catalog) × #3120. On GET /api/providers/[id]/models?refresh=true with an empty upstream result, persistDiscoveredModels([]) clears this connection's synced cache, but the handler's top-level providerSyncedModels snapshot (read before the refresh) was stale and leaked the just-cleared models back into the local_catalog fallback.

Fix

In the empty-discovery branch of buildApiDiscoveryResponse, re-read the provider's synced models so the response reflects the current (cleared) state — the union across the provider's remaining connections, or the static catalog when none remain. The normal (non-refresh) path keeps #3148's behavior untouched.

Validation (TDD — the existing test is the regression guard)

• provider models route clears cached discovery when a refresh returns no remote models → was red, now green.
• Full tests/unit/provider-models-route.test.ts suite: 54/54 (incl. the fix(providers): use synced models as fallback for all providers #3148 synced-authoritative test — no regression).
• typecheck:core clean, lint clean.

Release-blocker for v3.8.10 — needed before /generate-release.

[gemini-code-assist]

Code Review

This pull request updates the fallback local catalog logic in the model route handler to prevent stale synced models from leaking back into the response after an empty discovery. It re-derives the local catalog by fetching the remaining synced models or falling back to the static catalog. The review feedback suggests removing redundant type assertions when mapping the merged local catalog models, which will simplify the code and improve readability.

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[gemini-code-assist]

The type assertions as Record<string, unknown>, as string | undefined, and as string[] | undefined are redundant here. Since mergeLocalCatalogModels returns an array of objects extending LocalCatalogModel, the properties apiFormat and supportedEndpoints are already typed correctly and can be accessed directly. Removing these assertions simplifies the code and improves readability.

      const freshLocal = mergeLocalCatalogModels(freshRegistry, freshSpecialty).map((model) => ({
        id: model.id,
        name: model.name || model.id,
        ...(model.apiFormat ? { apiFormat: model.apiFormat } : {}),
        ...(model.supportedEndpoints ? { supportedEndpoints: model.supportedEndpoints } : {}),
        ...(freshRegistry.length > 0 ? { owned_by: provider } : {}),
      }));