[apapi]

Problem

In the AI Gateway page, opening 调用方式 for the cloud model
convaiinnovations/laya showed only chat-completions examples, even though
the gateway advertises it as typed-decisions (#241).

Two gaps caused it:

• AIGateway.tsx never passed isDecision / isDecisionOnly to
  ApiInfoDialog, so it always rendered the chat examples.
• Provider-scoped routes had no POST /providers/{providerID}/v1/decisions,
  so the URL in a decisions example would have returned 404.

Changes

• Gateway UI: cloud provider cards now pass the model's typed_decisions /
  decision_only flags to ApiInfoDialog. decisionsSupported is explicit
  and only true for the cloud provider; third-party providers and provider
  pools keep chat-only examples.
• Provider-scoped decisions route: POST /providers/{providerID}/v1/decisions
  is wired to the existing handler and honors the route source:
  /providers/csghub skips the local-first lookup, /providers/local requires
  a downloaded model, and third-party providers, pools, cluster and node
  routes return 400 decisions are only available for local and cloud models.
• Docs: openapi/local-api.json and its embedded copy document the new
  route; the route-family sync test covers it.
• Root POST /v1/decisions behavior is unchanged.

Testing

• go test ./internal/server — passes, including new cases for the cloud
  route, third-party provider rejection, pool rejection and local-route
  rejection.
• cd web && npm test — 23 files, 90 tests pass.
• cd web && npm run build — passes.
• Manual: fake AIGateway + browser. convaiinnovations/laya shows only the
  Decisions example with .../providers/csghub/v1/decisions; a chat model
  still shows chat examples; third-party/pool/local negative cases return 400.

web/dist is gitignored; it was rebuilt and synced into
internal/server/static only for local preview.

Fixes #241.