docs: regenerate translation reference and document the pages namespace

`content/docs/references/system/translation.mdx` is generated from the spec
schemas, so adding `pages` to `TranslationDataSchema` left it out of date
(caught by `@objectstack/spec check:docs`). Regenerated via
`gen:schema && gen:docs`.

`content/docs/ui/translations.mdx` is hand-written and enumerated the
translatable surfaces and the per-request metadata types — both stale as of
this branch. Added the `pages` row and `page` to the resolved-types list, plus
a note on why header copy is keyed by page name.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TubWYdWquVkS9dj733sDmC

Author: claude

content/docs/references/system/translation.mdx

@@ -197,6 +197,7 @@ Translation data for objects, apps, and UI messages
 | **validationMessages** | `Record<string, string>` | optional | Translatable validation error messages keyed by rule name (e.g., `{"discount_limit": "折扣不能超过40%"}`) |
 | **globalActions** | `Record<string, { label?: string; confirmText?: string; successMessage?: string; params?: Record<string, { label?: string; helpText?: string; placeholder?: string; options?: Record<string, string> }>; … }>` | optional | Global action translations keyed by action name |
 | **dashboards** | `Record<string, { label?: string; description?: string; actions?: Record<string, { label?: string }>; widgets?: Record<string, { title?: string; description?: string }> }>` | optional | Dashboard translations keyed by dashboard name |
+| **pages** | `Record<string, { label?: string; description?: string; title?: string; subtitle?: string }>` | optional | Page translations keyed by page name |
 | **settings** | `Record<string, { title?: string; description?: string; groups?: Record<string, { title?: string; description?: string }>; keys?: Record<string, { label?: string; help?: string; placeholder?: string; options?: Record<string, string> }>; … }>` | optional | Settings manifest translations keyed by namespace |
 | **metadataForms** | `Record<string, { label?: string; description?: string; sections?: Record<string, { label?: string; description?: string }>; fields?: Record<string, { label?: string; helpText?: string; placeholder?: string }> }>` | optional | Translations for metadata-type configuration forms keyed by metadata type |
 | **settingsCommon** | `{ sourceLabels?: object }` | optional | Cross-namespace Settings UI strings |

content/docs/ui/translations.mdx

@@ -73,10 +73,21 @@ export default defineStack({
 | Form sections | `objects.<name>._sections.<section>` |
 | App navigation | `apps.<app>.navigation.<id>.label` |
 | Dashboards and widgets | `dashboards.<name>` |
+| Page labels and `page:header` copy | `pages.<name>.label` / `description` / `title` / `subtitle` |
 | Global actions, settings, messages | `globalActions`, `settings`, `messages` |
 
-The metadata types resolved per request are **object, view, action, app, and
-dashboard** — a field's labels are translated as part of its object document.
+The metadata types resolved per request are **object, view, action, app,
+dashboard, and page** — a field's labels are translated as part of its object
+document.
+
+<Callout type="info">
+**Page headers are keyed by page name (#3589).** A page's `page:header`
+component has no stable id, so its `properties.title` / `properties.subtitle`
+are addressed through the page itself: `pages.<name>.title` / `subtitle`.
+`title` falls back to `pages.<name>.label`, so a page whose header title
+matches its nav label needs only `label`. Every `page:header` in the page's
+regions receives the same copy.
+</Callout>
 
 <Callout type="info">
 **One-shot result dialogs are translatable (#3347).** The post-success