Feat/code review system (#57)

## Summary
Complete code review system for reviewing git diffs with annotations.

### Features
- Interactive diff viewer with split/unified views
- Line-level annotation system
- Diff type selector (uncommitted, last commit, vs main branch)
- Dynamic default branch detection
- Empty state handling
- Simplified UX with streamlined feedback flow

Closes #51
Closes #56

packages/review-editor/package.json

@@ -0,0 +1,16 @@
+{
+  "name": "@plannotator/review-editor",
+  "version": "0.0.1",
+  "type": "module",
+  "exports": {
+    ".": "./App.tsx",
+    "./styles": "./index.css"
+  },
+  "dependencies": {
+    "@plannotator/ui": "workspace:*",
+    "@pierre/diffs": "^1.0.4",
+    "react": "^19.2.3",
+    "react-dom": "^19.2.3",
+    "tailwindcss": "^4.1.18"
+  }
+}