docs(spec): correct field.readonly describe re: import readonly-strip exemption (#3493)

The `field.readonly` describe said "system-context writes (import, seed replay,
migration) are exempt" — but a normal data import is NON-system (its writeCtx is
session-derived, isSystem:false) and still strips readonly fields. The strip is
bypassed only by `isSystem` writes (seed replay, migration) and, since #3497, by
an opt-in "historical" import (`preserveAudit`) that admits a whitelist (the
audit/timestamp family + author-declared business readonly fields). Fix the
describe accordingly and regenerate references/data/field.mdx.

Describe-string + regenerated reference doc only; no schema shape / behavior /
api-surface change. Empty changeset (releases nothing).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01B5rdfBKjkbcoEif4KUV6xE

Author: claude

.changeset/field-readonly-doc-preserveaudit.md

@@ -0,0 +1,4 @@
+---
+---
+
+docs(spec): correct the `field.readonly` describe re: import exemption (#3493). It listed "import" as a system-context exemption, but a normal data import is non-system and still strips; the strip is bypassed only by `isSystem` writes (seed replay, migration) and by an opt-in "historical" import (`preserveAudit`), which admits a whitelist. Describe-string only — regenerates `references/data/field.mdx`, releases nothing.

content/docs/references/data/field.mdx

@@ -145,7 +145,7 @@ const result = Address.parse(data);
 | **conditionalRequired** | `string \| { dialect: Enum<'cel' \| 'cron' \| 'template'>; source?: string; ast?: any; meta?: object }` | optional | Predicate (CEL) — field is required when TRUE. Alias of `requiredWhen`. |
 | **widget** | `string` | optional | Form widget override — names a registered field component (resolved as `field:<widget>`) to render this field instead of the `type` default. Degrades to the `type` renderer when unregistered. e.g. "object-ref", "filter-condition", "recipient-picker". |
 | **hidden** | `boolean` | optional | Hidden from default UI |
-| **readonly** | `boolean` | optional | Read-only — never editable in forms, AND server-enforced on BOTH write paths: a non-system write to this field is silently dropped from the payload on UPDATE (#2948/#3003) and on INSERT (#3043; a create can no longer directly seed e.g. `approval_status: "approved"`), symmetric with `readonlyWhen`. A stripped INSERT field still falls back to its `defaultValue`; system-context writes (import, seed replay, migration) are exempt. |
+| **readonly** | `boolean` | optional | Read-only — never editable in forms, AND server-enforced on BOTH write paths: a non-system write to this field is silently dropped from the payload on UPDATE (#2948/#3003) and on INSERT (#3043; a create can no longer directly seed e.g. `approval_status: "approved"`), symmetric with `readonlyWhen`. A stripped INSERT field still falls back to its `defaultValue`. Exempt from the strip: `isSystem` writes (seed replay, migration), and an opt-in "historical" import (`preserveAudit`, #3493) — which admits a whitelist (the audit/timestamp family plus author-declared business `readonly` fields). A normal (non-system) import is NOT system-context and still strips. |
 | **requiredPermissions** | `string[]` | optional | [ADR-0066 D3] Capabilities required to read/edit this field (mask on read, deny on write; AND-gate). |
 | **ackPlaintextMasking** | `boolean` | optional | [ADR-0100] Affirm a generic `password` field's plaintext-at-rest / masked-on-read contract is intended, silencing the author-time warning (#3420). No effect on non-password fields. |
 | **system** | `boolean` | optional | Auto-injected system/audit field (e.g. created_at, updated_by, organization_id). Tools that surface system fields separately from author-declared business fields should branch on this flag. |

packages/spec/src/data/field.zod.ts

@@ -502,7 +502,7 @@ export const FieldSchema = lazySchema(() => z.object({
 
   /** Security & Visibility */
   hidden: z.boolean().default(false).describe('Hidden from default UI'),
-  readonly: z.boolean().default(false).describe('Read-only — never editable in forms, AND server-enforced on BOTH write paths: a non-system write to this field is silently dropped from the payload on UPDATE (#2948/#3003) and on INSERT (#3043; a create can no longer directly seed e.g. `approval_status: "approved"`), symmetric with `readonlyWhen`. A stripped INSERT field still falls back to its `defaultValue`; system-context writes (import, seed replay, migration) are exempt.'),
+  readonly: z.boolean().default(false).describe('Read-only — never editable in forms, AND server-enforced on BOTH write paths: a non-system write to this field is silently dropped from the payload on UPDATE (#2948/#3003) and on INSERT (#3043; a create can no longer directly seed e.g. `approval_status: "approved"`), symmetric with `readonlyWhen`. A stripped INSERT field still falls back to its `defaultValue`. Exempt from the strip: `isSystem` writes (seed replay, migration), and an opt-in "historical" import (`preserveAudit`, #3493) — which admits a whitelist (the audit/timestamp family plus author-declared business `readonly` fields). A normal (non-system) import is NOT system-context and still strips.'),
 
   /**
    * [ADR-0066 D3] Capabilities required to READ/EDIT this field. A field