chore: mark US-028 as complete and update progress log

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

prd.json

@@ -499,7 +499,7 @@
         "Verify in browser using dev-browser skill"
       ],
       "priority": 28,
-      "passes": false,
+      "passes": true,
       "notes": ""
     },
     {

progress.txt

@@ -409,3 +409,15 @@
   - Apply consistent edge styling in both onConnect (new edges) and toReactFlowEdges (loaded edges)
   - Generate unique edge IDs with nanoid in onConnect callback
 ---
+
+## 2026-01-21 - US-028
+- What was implemented: Select and delete nodes functionality
+- Files changed:
+  - src/app/editor/[projectId]/FlowchartEditor.tsx - added deleteKeyCode prop to enable Delete/Backspace key deletion
+- **Learnings for future iterations:**
+  - React Flow has built-in node selection via clicking - no extra configuration needed
+  - Use `deleteKeyCode={['Delete', 'Backspace']}` prop to enable keyboard deletion
+  - React Flow automatically removes connected edges when a node is deleted (no manual cleanup needed)
+  - The useNodesState/useEdgesState hooks with onNodesChange/onEdgesChange handle all deletion state updates
+  - No explicit onNodesDelete callback is needed - the onNodesChange handler covers deletion events
+---