feat(spec): register FLOW_CONVERSION_CONFLICT in the ADR-0112 ledger (#9567 half 1)

`saveMetaItem`'s flow-conversion rename guard (protocol.ts:12674-12682) has
thrown a live 409 FLOW_CONVERSION_CONFLICT since ADR-0078 landed --
already SCREAMING_SNAKE, so this is an ordinary ADR-0112 D3 ledger
admission under @objectstack/metadata-protocol. It was invisible to
check:dispatcher-error-vocabulary's scan because the site stamps the code
through a cast rather than the bare-identifier `assign` shape the scan
matched.

Regenerated the two docs that mirror the ledger (content/docs/references/api/
contract.mdx, error-code-ledger.mdx) via gen:schema + gen:docs; check:generated
and check:docs both confirm no other artifact moved.

Half 2 of #9567 (`owd_widening_forbidden`) is measurement-only in this PR --
see the PR description -- so this PR does not close the issue.

Part of #9567

Author: claude

.changeset/register-flow-conversion-conflict.md

@@ -0,0 +1,13 @@
+---
+"@objectstack/spec": patch
+---
+
+Register `FLOW_CONVERSION_CONFLICT` (409) in the ADR-0112 error-code ledger under
+`@objectstack/metadata-protocol` (#9567). The code was already live on the wire —
+`saveMetaItem`'s flow-conversion rename guard (`protocol.ts`) has thrown it since
+ADR-0078 landed, already SCREAMING_SNAKE — but was invisible to
+`check:dispatcher-error-vocabulary`'s scan because the site stamps it through a
+cast (`(err as any).code = 'FLOW_CONVERSION_CONFLICT'`) rather than the bare-
+identifier `assign` shape the scan matched at the time. This is an ordinary,
+additive admission: no accept/reject behavior, no producer, and no wire shape
+changes.

content/docs/references/api/contract.mdx

@@ -27,7 +27,7 @@ const result = ApiErrorSchema.parse(data);
 
 | Property | Type | Required | Description |
 | :--- | :--- | :--- | :--- |
-| **code** | `Enum<'VALIDATION_ERROR' \| 'INVALID_FIELD' \| 'MISSING_REQUIRED_FIELD' \| 'INVALID_FORMAT' \| 'VALUE_TOO_LONG' \| 'VALUE_TOO_SHORT' \| 'VALUE_OUT_OF_RANGE' \| … +285 more>` | ✅ | Error code (e.g. VALIDATION_ERROR; StandardErrorCode ∪ the ledger the serving side registers — ERROR_CODE_LEDGER for framework packages) |
+| **code** | `Enum<'VALIDATION_ERROR' \| 'INVALID_FIELD' \| 'MISSING_REQUIRED_FIELD' \| 'INVALID_FORMAT' \| 'VALUE_TOO_LONG' \| 'VALUE_TOO_SHORT' \| 'VALUE_OUT_OF_RANGE' \| … +286 more>` | ✅ | Error code (e.g. VALIDATION_ERROR; StandardErrorCode ∪ the ledger the serving side registers — ERROR_CODE_LEDGER for framework packages) |
 | **declaredCode** | `string` | optional | The producer-declared code, verbatim, when it is not a member of the closed `code` vocabulary — the open, author-authored channel (app-specific spellings; ADR-0112, #9106) |
 | **message** | `string` | ✅ | Readable error message |
 | **category** | `string` | optional | Error category (e.g. validation, authorization) |
@@ -179,6 +179,7 @@ const result = ApiErrorSchema.parse(data);
 * `FILE_NOT_FOUND`
 * `FILTER_TOKEN_UNKNOWN`
 * `FILTER_TOKEN_UNRESOLVED`
+* `FLOW_CONVERSION_CONFLICT`
 * `FLOW_DISABLED`
 * `FLOW_FAILED`
 * `FLOW_NO_START_NODE`

content/docs/references/api/error-code-ledger.mdx

@@ -284,6 +284,7 @@ const result = ErrorCode.parse(data);
 * `FILE_NOT_FOUND`
 * `FILTER_TOKEN_UNKNOWN`
 * `FILTER_TOKEN_UNRESOLVED`
+* `FLOW_CONVERSION_CONFLICT`
 * `FLOW_DISABLED`
 * `FLOW_FAILED`
 * `FLOW_NO_START_NODE`

packages/spec/src/api/error-code-ledger.zod.ts

@@ -377,6 +377,19 @@ export const ERROR_CODE_LEDGER = {
     'COMMIT_NOT_FOUND',
     'CONCURRENT_UPDATE',
     'DESTRUCTIVE_CHANGE',         // change would drop data; needs an explicit opt-in
+    // [#9567] ADR-0078's rename guard refuses a metadata write whose `type`/
+    // `name` token is already a LIVE name owned by something else in the
+    // environment — persisting the un-renamed body would mint exactly the row
+    // that guard exists to prevent (`saveMetaItem`, `protocol.ts`, same posture
+    // as `duplicatePackage` / #4454). 409, not 422: the body may be perfectly
+    // valid — the refusal comes from environment state, so resubmitting the
+    // same body cannot help. Surfaced by the widened
+    // `check:dispatcher-error-vocabulary` scan (#9460, half 1); NOTE the
+    // producer's message prefix spells the code lowercase
+    // (`[flow_conversion_conflict]`) while the wire stamp is SCREAMING_SNAKE —
+    // a human-log inconsistency worth a glance, left as-is because the
+    // producer is outside this ledger's surface.
+    'FLOW_CONVERSION_CONFLICT',
     'INVALID_METADATA',
     'INVALID_REQUEST',
     'ITEM_LOCKED',                // _lock refuses the write/delete (ADR-0010 §3.3)