docs(spec): regenerate contract.mdx and error-code-ledger.mdx on the merged tree

Discharges the os-regen deferral the merge commit recorded. Generated by
`pnpm --filter @objectstack/spec build` then
`pnpm --filter @objectstack/spec gen:docs` (packages/spec/scripts/build-docs.ts);
a second gen:docs run is a no-op and check:docs reports 226 files in sync.
The regenerated hunks are this branch's own on origin/main's side:
the CONCURRENT_LIMIT_EXCEEDED rows leave the StandardErrorCode lists and the
two enum summaries count one member fewer.

Claude-Session: https://claude.ai/code/session_01AsCNgFBs8HCjwhyHQsFbx3
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude

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' \| … +322 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' \| … +321 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) |
 | **message** | `string` | ✅ | Readable error message |
 | **userMessage** | `string` | optional | Producer-marked user-facing refusal text, verbatim. Present exactly when the producer opted in at throw time; consumers render it to end users and keep their generic substitution for anything unmarked. Status-agnostic; never replaces `message`. |
@@ -80,7 +80,6 @@ const result = ApiErrorSchema.parse(data);
 * `PRECONDITION_REQUIRED`
 * `RATE_LIMIT_EXCEEDED`
 * `QUOTA_EXCEEDED`
-* `CONCURRENT_LIMIT_EXCEEDED`
 * `INTERNAL_ERROR`
 * `DATABASE_ERROR`
 * `TIMEOUT`

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

@@ -247,7 +247,6 @@ const result = ErrorCode.parse(data);
 * `PRECONDITION_REQUIRED`
 * `RATE_LIMIT_EXCEEDED`
 * `QUOTA_EXCEEDED`
-* `CONCURRENT_LIMIT_EXCEEDED`
 * `INTERNAL_ERROR`
 * `DATABASE_ERROR`
 * `TIMEOUT`
@@ -560,7 +559,7 @@ const result = ErrorCode.parse(data);
 | Property | Type | Required | Description |
 | :--- | :--- | :--- | :--- |
 | **code** | `string` | ✅ | The registered extension code the waiver keeps admissible |
-| **shadows** | `Enum<'VALIDATION_ERROR' \| 'INVALID_FIELD' \| 'MISSING_REQUIRED_FIELD' \| 'INVALID_FORMAT' \| 'VALUE_TOO_LONG' \| 'VALUE_TOO_SHORT' \| 'VALUE_OUT_OF_RANGE' \| … +43 more>` | ✅ | The standard-catalog member whose condition the code re-spells |
+| **shadows** | `Enum<'VALIDATION_ERROR' \| 'INVALID_FIELD' \| 'MISSING_REQUIRED_FIELD' \| 'INVALID_FORMAT' \| 'VALUE_TOO_LONG' \| 'VALUE_TOO_SHORT' \| 'VALUE_OUT_OF_RANGE' \| … +42 more>` | ✅ | The standard-catalog member whose condition the code re-spells |
 | **reason** | `string` | ✅ | Why the synonym stays registered — recorded so admission is a decision, not drift |
 
 ### Allowed Values: `StandardSynonymWaiver.shadows`
@@ -606,7 +605,6 @@ const result = ErrorCode.parse(data);
 * `PRECONDITION_REQUIRED`
 * `RATE_LIMIT_EXCEEDED`
 * `QUOTA_EXCEEDED`
-* `CONCURRENT_LIMIT_EXCEEDED`
 * `INTERNAL_ERROR`
 * `DATABASE_ERROR`
 * `TIMEOUT`