docs(project-editor): document Sprint 16 tabs, draft/publish gap, and validation rules

docs/Project-Editor.md

@@ -88,6 +88,14 @@ Future backend integration:
   - export JSON
   - import JSON
   - runtime preview without full browser refresh
+- Languages (Sprint 16)
+  - add/remove supported locale
+  - set default locale
+  - generically syncs translation keys across static pages and navigation labels (`LocaleSyncService`)
+- Navigation (Sprint 16)
+  - header navigation: add/remove/reorder/edit label/URL/visibility
+  - flat footer navigation: same actions
+  - grouped footer navigation (column-based) is read-only in this tab for now
 
 ## Preview Strategy
 
@@ -120,15 +128,36 @@ Current widget editor supports explicit fields for:
 
 Other widgets use JSON props fallback until dedicated editors are added.
 
-## Future Backend Endpoints
+## Draft / Publish (Sprint 16)
 
-Recommended future builder endpoints:
-- `GET /builder/bootstrap`
-- `PUT /builder/bootstrap`
-- `POST /builder/bootstrap/preview`
-- `POST /builder/bootstrap/validate`
-- `POST /builder/bootstrap/import`
-- `GET /builder/bootstrap/export`
+There is still no backend draft/publish API. This sprint models it client-side
+in `ProjectEditorFacade`:
+- `status: 'draft' | 'published'` and `dirty` (diffed against the
+  last-saved snapshot) live in facade state.
+- `save()` snapshots the current in-memory bootstrap as "last saved" (no
+  network call yet).
+- `publish()` runs `ProjectValidator`, and if there are no issues, applies
+  the bootstrap via `PlatformRuntimeService.reloadFromBootstrap` and marks
+  status `published`.
+
+**Backend gap, not yet implemented:** real persistence needs
+`PUT /builder/bootstrap/draft` and `POST /builder/bootstrap/publish`
+endpoints so drafts/publishes survive a reload and are shared across editors.
+
+## Validation
+
+`ProjectValidator` (`services/project-validator.service.ts`) runs on every
+render of the save bar: missing logo, no languages, invalid marketplace URL,
+duplicate static-page slugs, empty homepage, a homepage widget with no
+`type`, duplicate header navigation links, invalid theme colors. Publish is
+blocked while any issue is present; Save is not.
+
+## Rich HTML editing
+
+Static page HTML is edited via `MarketplaceHtmlEditorComponent`
+(`components/html-editor/`), a `contentEditable` + toolbar component with no
+external dependency. It emits raw HTML on every change and never sanitizes —
+sanitization remains a storefront-render concern.
 
 ## Constraints