feat(plugin): filter published catalog by provider with empty-result guard

[maxmad64bis]

⚠️ base-red inherited: #15306

Summary

Adds an opt-in providersAllow option to the v2 plugin that restricts the published catalog (models, combos, auto-combos) by provider id prefix; empty or absent means the full catalog, so existing installs are unchanged.

Related Issues

• Related to feat(plugin): filter published catalog by capability presets #14554

Validation

• Change type: other
• Focused tests and category gates from the golden path — 8/8 touched-file tests green, each new case fails without the change
• npm run lint — ESLint on the touched files is clean; the full run is red on the base (🔴 Release branch not green: release/v3.8.52 #15306).
• Reconciled with the current active release base; focused checks rerun afterward
• Production-code changes include a new or updated automated test in this PR

Tests Added Or Updated

• @omniroute/opencode-plugin-v2/tests/provider-filter.test.ts (new): predicate-level coverage — empty allow, single provider, unknown name fail-open, empty-result case, multi-provider combos, pool typo, alias/canonical resolution, normalization.
• @omniroute/opencode-plugin-v2/tests/catalog-provider.test.ts (new): integration through parsePluginOptions + the exported toResolvedOptions into collectCatalog — all spec cases at catalog level plus synthetic scale and allowlist interop.
• @omniroute/opencode-plugin-v2/tests/options.test.ts (extended): option default, acceptance, non-array rejection.

Coverage Notes

• New module src/provider-filter.ts is pure (no fetch, no global state) and covered at both predicate and catalog levels; src/catalog.ts wiring (3 collection points + empty-result guard) is covered by the integration file.
• Red proofs: removing any one of the three predicates or the empty-result guard makes the corresponding tests fail.

Reviewer Notes

• Behavior: Vocabulary-free runs are inert by design: with no vocabulary the filter warns once and keeps the full catalog; unknown prefixes always pass. Only a known-but-absent name triggers the empty-result path. A combo passes when any member passes (unlike the capability filter, which requires all members).
• Merge: Node 24 CI red (staged-refresh, "refresh after TTL keeps the overlay") not reproduced locally: 10/10 green on base and head with the same Node 24.21.0 binary — looks like CI flake, out of scope here. Merge order with feat(plugin): filter published catalog by capability presets #14554: this one first (additive, opt-in), feat(plugin): filter published catalog by capability presets #14554 reconnects on top — both touch the same three collection points, so the second to merge resolves the overlap. Shares the plugin catalog, options and README with feat(plugin): filter published catalog by capability presets #14554: either order, with a rebase on the release tip; fix(plugin): stop requesting the retired virtual-entries route #15392 is stacked on this branch and lands after it. feat(plugin): publish useful catalog entries by default, full list on request #15484 lands after this one, with a rebase on conflict.