Metadata kinds without a code-authoring surface: trigger, router, function, service, external_catalog

[os-zhuang]

While upgrading the showcase to a registry-driven coverage manifest (every kind in DEFAULT_METADATA_TYPE_REGISTRY must be demonstrated or explicitly waived), five kinds turned out to have no declarative authoring surface an example app could use:

• trigger — registry entry + file patterns exist, but there is no stack collection / defineTrigger helper wired through defineStack. Record-change triggering is demonstrated behaviorally in the showcase via record-change flows (requires: ['triggers']), not as standalone trigger artifacts.
• router / function / service — code-only by design (allowRuntimeCreate: false). The showcase's code-level equivalent is the imperative HTTP mount in examples/app-showcase/src/system/server/recalc-endpoint.ts. If these kinds are meant to stay code-only, consider saying so in the registry docs; if they're meant to become declarative someday, this issue tracks the gap.
• external_catalog — runtime-created via Setup → Datasources → Sync (ADR-0062); there is no declarative artifact an app package can ship. The showcase demos the flow that produces one (external datasource federation), not the artifact itself.

These five are recorded as explicit waivers in examples/app-showcase/src/coverage.ts (KIND_COVERAGE) pointing at this issue, so the coverage test stays green without faking coverage (Prime Directive #10).

Done means, per kind: either (a) a declarative authoring surface lands and the showcase demonstrates it, or (b) the registry/docs explicitly mark the kind code-only/runtime-only and the waiver is converted into a permanent, documented exclusion.

[os-zhuang]

Assessment after auditing the actual runtime consumers — concrete recommendation per kind:

Admission test (the kind-level analogue of ADR-0085 §2): a metadata kind earns its registry entry only with ① an independent lifecycle, ② declarative governability (repository/versioning/overlay semantics), ③ a real consumer.

• trigger — retire. "Data change → reaction" already has two delivered mechanisms with clean separation: hook (sync, data layer, in-transaction, 24 lifecycle events) and record_change flows (async, business layer, observable — ADR-0018/0020). trigger has no stack collection, no define helper, no FS loader (verified: nothing loads *.trigger.*), no executor. It is a Salesforce Apex-Trigger legacy slot; keeping it invites a third overlapping mechanism.
• router / function / service — retire. Their real, consumed forms already live elsewhere: router → plugin contributes.routes (HttpDispatcher) + the app-facing declarative apis: (demonstrated in the showcase since Examples cleanup: slim app-crm to its smoke core, migrate apis: to showcase, app-todo truth pass #2624); function → defineStack({ functions }) code values (hook-binder / flow script body runners) + plugin contributes.functions; service → the plugin system itself. These are code contributions, and every governance flag on their registry entries is already "no" (allowRuntimeCreate: false, no overlay, no loader). If Studio needs a catalog view of registered routes/functions/services, that is runtime introspection — a read-only endpoint, not a metadata kind. If a future "AI-authorable serverless function artifact" materializes (ADR-0087 direction), add it back then with a full design — an empty kind today only misleads AI authors reading the registry.
• external_catalog — keep, and its lack of an authoring surface is CORRECT. It is a derived runtime snapshot of a federated datasource's remote schema (ADR-0062) with a real lifecycle (sync refresh, mismatch policy). Shipping one in a package would be stale on arrival — like shipping a build artifact as source. Mark it runtime-created in the registry docs and convert the showcase waiver to a permanent, documented exclusion.

Proposed resolution: one small ADR that (1) states the kind admission test, (2) retires trigger/router/function/service from MetadataTypeSchema + DEFAULT_METADATA_TYPE_REGISTRY (pre-launch, no compat debt — 30 kinds → 26), (3) documents external_catalog as runtime-created. The showcase's registry-driven coverage test then forces the manifest to shrink in lockstep, and this issue closes.

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