feat: complete code cleanup and create feature parity plan

Major Architecture Improvements:
- Separate JavaScript library (lib/) with proper build system
- Go CLI with embedded library using go:embed
- Hot reload development with Air integration
- Library + CLI build pipeline with npm run build

Code Cleanup:
- Remove obsolete assets (insertr-cli/assets/editor/)
- Clean up package.json metadata and dependencies
- Update .gitignore for new architecture
- Remove unused 'marked' dependency

New Documentation:
- Add comprehensive TODO.md with feature gap analysis
- Document critical gaps between prototype and current library
- Create phased implementation plan for feature parity
- Update DEVELOPMENT.md with hot reload workflow
- Add LIBRARY.md documenting new architecture

Hot Reload System:
- Air watches both Go CLI and JavaScript library
- Library changes trigger: rebuild → copy → CLI rebuild → serve
- Seamless development experience across full stack

Next Steps:
- Current library is basic proof-of-concept (prompt() editing)
- Archived prototype has production-ready features
- Phase 1 focuses on professional forms and authentication
- Phase 2 adds validation and content persistence

lib/package.json

@@ -0,0 +1,30 @@
+{
+  "name": "@insertr/lib",
+  "version": "1.0.0",
+  "type": "module",
+  "description": "The Tailwind of CMS - Client-side library for content injection and editing",
+  "main": "dist/insertr.js",
+  "module": "src/index.js",
+  "files": [
+    "dist/",
+    "src/"
+  ],
+  "scripts": {
+    "build": "rollup -c",
+    "watch": "rollup -c -w",
+    "dev": "rollup -c -w"
+  },
+  "keywords": [
+    "cms",
+    "content",
+    "headless",
+    "inline-editing"
+  ],
+  "author": "Insertr Team",
+  "license": "MIT",
+  "devDependencies": {
+    "@rollup/plugin-node-resolve": "^15.0.0",
+    "@rollup/plugin-terser": "^0.4.0",
+    "rollup": "^3.0.0"
+  }
+}