docs(fixtures): mark installed-base deleteBehavior fixtures as the pre-#9784 era; add changeset

The two #4447 audit-governance fixtures pin the PRE-#9784 artifact shape
(materialized deleteBehavior on a datetime) — artifacts of that shape
remain in the installed base and must keep loading, so the bytes stay;
the comments now say which era they are. Changeset: @objectstack/spec
minor.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rxnd8cyFnoU8V5y21PaTsy

Author: claude

.changeset/field-deletebehavior-reference-only.md

@@ -0,0 +1,32 @@
+---
+"@objectstack/spec": minor
+---
+
+feat(spec): materialize `deleteBehavior` only on reference field types (#9784)
+
+`FieldSchema` no longer materializes the `deleteBehavior: 'set_null'` default
+onto non-reference field types (`text` / `datetime` / `number` / every other
+non-relational type, `user` included). The key has no meaning there — the
+engine's `cascadeDeleteRelations` reads it exclusively on `master_detail` /
+`lookup` fields carrying a `reference` — yet the materialized default shipped
+in every built app artifact, where a parse-time default becomes an apparent
+explicit declaration downstream (the #4447 shadowing mechanism) and reads as
+meaningful to AI authors browsing the artifact.
+
+What changes and what does not:
+
+- **Bare non-reference fields** parse to output that **omits** `deleteBehavior`
+  (previously: `deleteBehavior: 'set_null'` materialized on every type). Built
+  artifacts thin accordingly — measured on the showcase app: 210 fields, the
+  key drops from 206 fields to 16.
+- **`lookup` and `tree`** keep materializing `set_null` byte-identically, at
+  shape position.
+- **`master_detail`** keeps omitting it (the #9689 idempotent-materialization
+  ruling, unchanged).
+- **The accept-set is untouched**: an authored `deleteBehavior` on any field
+  type parses exactly as before and round-trips verbatim, so artifacts built
+  by earlier versions (which carry the materialized key on every field) remain
+  fully legal inputs. `parse(parse(x))` holds across the boundary.
+
+No authored metadata needs any change: no key is removed, renamed or
+re-shaped, and no authoring spelling that parsed before is refused now.

packages/metadata-protocol/src/protocol.audit-field-governance.test.ts

@@ -129,6 +129,11 @@ function makeStubEngine() {
  * spelled `false` on two of the four and left ABSENT on the other two, because
  * absent defaults to false as well and the read must not be right only for the
  * spelling that happens to be explicit.
+ *
+ * `deleteBehavior: 'set_null'` on the datetime is the PRE-#9784 materializing
+ * era — newly built artifacts omit the key on non-reference fields, but
+ * artifacts of this shape remain in the installed base and must keep loading;
+ * keep the bytes as they shipped.
  */
 const artifactObject = (name: string) => ({
     name,

packages/objectql/src/engine-audit-anchor-write.test.ts

@@ -244,7 +244,12 @@ describe('[#4447] a declared audit field cannot loosen the platform posture', ()
     fields: {
       id: { name: 'id', label: 'ID', type: 'text' as const, primaryKey: true },
       title: { name: 'title', label: 'Title', type: 'text' as const },
-      // Verbatim from examples/app-showcase/dist/objectstack.json.
+      // Verbatim from the PRE-#9784 examples/app-showcase/dist/objectstack.json
+      // — the materializing era, when FieldSchema baked `deleteBehavior:
+      // 'set_null'` onto every type. Newly built artifacts omit the key on
+      // non-reference fields (#9784), but artifacts of this shape remain in
+      // the installed base and this suite pins that they cannot loosen audit
+      // governance — keep the bytes as they shipped.
       created_at: {
         label: 'Created At', type: 'datetime' as const, required: false,
         searchable: false, multiple: false, unique: false,