XPath query for node selection (#82)
* Add XPath query for node selection
- packages/core/src/xpath.ts: XPath engine using fontoxpath with custom
DOM facade over SceneGraph nodes
- RPC command: 'query' with selector, page, limit params
- CLI command: 'open-pencil query <file> <xpath>' with --json, --page, --limit
- AI/MCP tool: 'query_nodes' with XPath examples in description
- Queryable attributes: name, width, height, x, y, visible, opacity,
cornerRadius, fontSize, fontFamily, fontWeight, layoutMode, itemSpacing,
padding*, strokeWeight, rotation, locked, blendMode, text, lineHeight,
letterSpacing
* Add tests and docs for XPath query
- 9 unit tests for queryByXPath/matchByXPath core functions
- 6 tool tests for query_nodes AI/MCP tool
- README: query examples in CLI section
- VitePress docs: patterns, queryable attributes, example output
- CHANGELOG: feature entry
* Lazy-load fontoxpath to avoid bundling in desktop app
- Dynamic import() instead of static import for fontoxpath
- queryByXPath/matchByXPath now async (they were sync before)
- RpcCommand.execute allows R | Promise<R> for async commands
- Fix 2 lint errors (unnecessary optional chain, always-truthy)
- Update all tests and CLI to await results
f2ef9c976d