Inspect provider integration install-consent gate

Returns a read-only install-consent gate for a connected app when the authenticated automation client has provider_integrations.manage. External URL: /v1/providers/current/integrations/{appId}/install-gate. Current Next.js implementation path: /api/platform/v1/providers/current/integrations/[appId]/install-gate. This read-only route does not require Idempotency-Key; it exposes consent copy, required scopes, data categories, prerequisite evidence, and a fail-closed gate decision only. It never returns raw credentials, OAuth tokens, webhook secrets, raw sync payloads, customer PII, direct external-system calls, install mutations, pause/resume mutations, or revocation mutations.