Complete library cleanup and documentation overhaul

## Library Code Cleanup (~1,200+ lines removed)
- Remove legacy markdown system (markdown.js, previewer.js)
- Delete unused EditContext code from ui/editor.js (~400 lines)
- Remove version history UI components from form-renderer.js (~180 lines)
- Clean unused CSS styles from insertr.css (~120 lines)
- Update package.json dependencies (remove marked, turndown)

## Documentation Updates
- README.md: Update from markdown to HTML-first approach
- AGENTS.md: Add current architecture guidance and HTML-first principles
- TODO.md: Complete rewrite with realistic roadmap and current status
- demos/README.md: Update for development demo server usage

## System Reality Alignment
- All documentation now reflects current working system
- Removed aspirational features in favor of actual capabilities
- Clear separation between development and production workflows
- Accurate description of style-aware editor with HTML preservation

## Code Cleanup Benefits
- Simplified codebase focused on HTML-first approach
- Removed markdown conversion complexity
- Cleaner build process without unused dependencies
- Better alignment between frontend capabilities and documentation

Ready for Phase 3a server updates with clean foundation.

demos/simple/index.html

@@ -43,10 +43,15 @@
         }
         
         .fancy {
-            color: #7c3aed;
+            color: #059660;
             text-decoration: none;
             border-bottom: 2px solid #a855f7;
         }
+
+        .fancy:visited {
+            color: #509;
+            border: 1px solid red
+        }
         
         .fancy:hover {
             background: #ede9fe;
@@ -180,4 +185,4 @@
         <p class="insertr">Need help? Contact our <a id="support-link" class="fancy" href="mailto:support@example.com" title="Email our support team">support team</a> anytime.</p>
     </div>
 </body>
-</html>
+</html>