feat: add excalidraw extension with live diagram preview (#75)

* test: include extension tests in test script

* refactor(excalidraw): extract prompts to standalone markdown files

* docs: update changelog

Author: kostyay

package.json

@@ -10,7 +10,7 @@
   "type": "module",
   "scripts": {
     "lint": "eslint --fix pi-extensions/ tests/ && npx tsc --noEmit",
-    "test": "npm run lint && node --experimental-strip-types --test tests/*.test.ts"
+    "test": "npm run lint && node --experimental-strip-types --test tests/*.test.ts pi-extensions/**/*.test.ts"
   },
   "keywords": [
     "pi-package",

pi-extensions/excalidraw/CHANGELOG.md

@@ -0,0 +1,8 @@
+# Changelog
+
+All notable changes are documented here.
+
+
+## test/extend-test-coverage
+
+Extended test coverage to the Excalidraw extension by integrating extension tests into the main test script (#75). Refactored Excalidraw prompt content into standalone markdown files (`element-format.md`, `draw-instruction.md`) for better maintainability and modularity. Implemented a comprehensive Excalidraw diagram preview tool with `draw_diagram` and `save_diagram` capabilities, streaming element rendering with throttling, checkpoint management for diagram persistence, and clipboard export (PNG/SVG). The extension includes a webview-based live preview window powered by @excalidraw/excalidraw with support for macOS PNG clipboard operations and graceful error handling for partial JSON streaming.