feat(ci): add api-reference sync agent workflow (#676)

.github/templates/api-reference-update-issue.md

@@ -0,0 +1,40 @@
+<!-- component:{{COMPONENT_NAME}} -->
+<!-- trigger-prs:{{TRIGGER_PR_NUMBERS}} -->
+<!-- trigger-issues:{{TRIGGER_ISSUE_NUMBERS}} -->
+
+## Summary
+API reference update needed for `{{COMPONENT_NAME}}` based on recent merged PR changes.
+
+## References
+- Triggering PR(s): {{SOURCE_PR_URLS}}
+- Triggering issue(s): {{SOURCE_PR_ISSUE_URLS}}
+
+## API Changes Summary
+| Surface | Change Type | Before | After | Source |
+|---|---|---|---|---|
+{{API_CHANGES_TABLE_ROWS}}
+
+## Out-of-Sync Docs
+| Doc Location | Drift Type | Current | Expected | Action |
+|---|---|---|---|---|
+{{OUT_OF_SYNC_TABLE_ROWS}}
+
+## Documentation Notes
+- Conventions check (props/state/data attrs/css vars): {{CONVENTION_STATUS}}
+- JSDoc completeness for interface fields: {{JSDOC_STATUS}}
+- Planning metadata copied from source issue:
+  - Milestone: {{MILESTONE_STATUS}}
+  - Project board(s): {{PROJECT_STATUS}}
+
+## Implementation Notes
+- Target files: {{TARGET_FILES_LIST}}
+- Drift-specific tasks: {{IMPLEMENTATION_TASKS}}
+- Validation commands:
+  - `pnpm -C site api-docs`
+  - `pnpm -C site build`
+
+## Scope Checklist
+- [ ] Update reference page content for `{{COMPONENT_NAME}}`.
+- [ ] Update sidebar entries in `site/src/docs.config.ts` if required.
+- [ ] Regenerate API reference JSON (`pnpm -C site api-docs`).
+- [ ] Verify build (`pnpm -C site build`).