fix(metadata): route the three read-side /meta verbs through the canonical type boundary (#9157)

.changeset/read-verb-canonical-meta-type-fold.md

@@ -0,0 +1,56 @@
+---
+"@objectstack/metadata-protocol": patch
+---
+
+fix(metadata): the three read-side `/meta` verbs reach the canonical type boundary — history, audit and references (#9157)
+
+<!-- adr-0087: not-required (no-migration-prescription) No authorable key is
+added, renamed, retired or tombstoned. This routes three existing protocol
+methods through an existing request-boundary function; the only externally
+visible movement is on three GET routes, described below. -->
+
+Step ① of the maintainer ruling in #9180 (2026-08-16): **the `/meta` type
+segment is singular, always.**
+
+`auditMetaItem`, `historyMetaItem` and `findReferencesToMeta` each opened by
+deriving their type key from `PLURAL_TO_SINGULAR` — the MANIFEST-COLLECTION map
+that #7894 moved this boundary off — instead of calling
+`canonicalizeMetaRequestType`, which the nine sibling `/meta` verbs already
+call. That one call carries **both** the URL spelling map **and**
+`metaUrlSpellingRefusal`, and the refusal is the half these three could never
+reach: it lives *inside* the function they skipped.
+
+**What changes on the wire**, on `GET /api/v1/meta/:type/:name/history`,
+`…/audit` and `…/references`:
+
+| caller's `:type` | before | after |
+| --- | --- | --- |
+| `viewes` — an unrecognised spelling of a **declared** type | 200 with an empty body | **400 `INVALID_REQUEST`**, naming both accepted spellings (`view`, `views`) |
+| `translations`, `fields`, `seeds`, `external_catalogs` — recognised plurals of the four types absent from the manifest map | 200 with an empty body | 200 with the **real** rows |
+| `views` — a recognised plural already in the manifest map | unchanged | unchanged |
+| `fieldz` — reaches for no declared type | unchanged | unchanged; the refusal stays narrow, so a plugin-registered kind can never trip it |
+
+The harm being closed is the empty-accumulator shape: a plural read answered
+`{ "events": [] }` / `{ "references": [] }` — read by an operator as *"nothing
+depends on this"* — at exactly the moment they were about to rename or delete.
+**Loudly wrong beats quietly lying**, so a spelling the platform cannot honour
+is now refused with the canonical one named rather than answered emptily.
+
+Two measured details worth stating, because both invert an intuition:
+
+- On `historyMetaItem` the unfolded plural was not merely a wrong key, it was a
+ door **around** a gate. `field` declares neither `allowOrgOverride` nor
+ `allowRuntimeCreate`, so the canonical spelling is refused by the overlay gate
+ and never reaches the store — while `fields` took
+ `isRuntimeCreateAllowed`'s no-static-registry-entry arm (the plugin path,
+ permissive by construction) and issued a real `sys_metadata_history` read
+ keyed `'fields'`. Same empty body, opposite path.
+- On `findReferencesToMeta` the refusal is the **whole** visible change. Every
+ `REFERENCE_PATHS` key is manifest-present and already folded, so a
+ manifest-absent target still answers `{ "references": [] }` — which that
+ method documents as a legitimate no-hit. Widening that registry is a coverage
+ question, not a spelling one.
+
+Recognised plural spellings are **not** retired here — `metaUrlSpellingRefusal`
+returns `null` for `views` and for `translations`, and a pin asserts it. That is
+#9180 step ③, which the ruling requires to stay independently revertible.