Milestone 5 of the Configuration Engine sprint.
- Facade: changeSummary computed - per modified field, before/after values
(schema label + stringified diff vs originalBootstrap), reusing
modifiedFields from M4.
- preview-section: new "changes since last publish" card ahead of the
existing export/import/live-preview card - validation issue list
(warning/error styled) plus a before/after change table. Reuses the
existing, non-destructive ProjectEditorPreviewService.preview() call.
- i18n: previewChangesTitle/NoIssues/NoChanges/ChangeField/Before/After in
interface + en/ru/hy.
Gate: tsc --noEmit, npm test (33/33), arch:check, build all green.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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