chore: mark US-019 as complete and update progress log

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

prd.json

@@ -335,7 +335,7 @@
         "Verify in browser using dev-browser skill"
       ],
       "priority": 19,
-      "passes": false,
+      "passes": true,
       "notes": ""
     },
     {

progress.txt

@@ -292,3 +292,16 @@
   - Use position="bottom-right" prop to position controls in bottom-right corner
   - Pan (click-and-drag) and zoom (mouse wheel) are React Flow defaults, no extra config needed
 ---
+
+## 2026-01-21 - US-019
+- What was implemented: Editor toolbar with add/save/export/import buttons
+- Files changed:
+  - src/components/editor/Toolbar.tsx - new toolbar component with styled buttons
+  - src/app/editor/[projectId]/FlowchartEditor.tsx - integrated toolbar with placeholder handlers
+- **Learnings for future iterations:**
+  - Toolbar component accepts callback props for actions (onAddDialogue, onSave, etc.)
+  - Node type buttons use color coding: blue (Dialogue), green (Choice), orange (Variable)
+  - Action buttons (Save, Export, Import) use neutral bordered styling
+  - FlowchartEditor now uses flex-col layout to stack toolbar above canvas
+  - Placeholder handlers with TODO comments help track future implementation work
+---