feat: complete prediction UI feedback tasks (11.2, 11.4, 11.5)

- Implement disagreement visual highlighting with distinct colors
  - Yellow highlight for 'missed_by_human' predictions
  - Orange for 'label_mismatch' disagreements
  - Warning icon on disagreement markers
- Add click-to-convert prediction feedback
  - Click disagreement predictions to create span annotations
  - Auto-fill with predicted label and times
  - Set source as 'model_confirmed' or 'model_corrected'
- Add dismiss action for false positive predictions
  - Alt+Click or Ctrl+Click to dismiss predictions
  - Saves negative annotation with label 'O'
  - Records original prediction in model_prediction field
- Filter predictions when 'Show only disagreements' is enabled

openspec/changes/line-rectangle-annotations/tasks.md

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+## 1. Enhance TrendLine Plugin
+
+- [ ] 1.1 Add `hitTest(x, y)` method to `TrendLine` class — calculate perpendicular distance from click point to line segment in pixel coordinates, return `PrimitiveHoveredItem` with annotation ID if within 10px tolerance
+- [ ] 1.2 Add `setSelected(isSelected)` method and selection state to `TrendLine` — when selected, renderer draws thicker line and circular endpoint handles (radius 6px, white fill, colored stroke)
+- [ ] 1.3 Add `attached()/detached()` lifecycle methods to `TrendLine` to store `SeriesAttachedParameter` reference (needed for hitTest coordinate conversion)
+- [ ] 1.4 Add preview line support — dashed stroke style and reduced opacity when an `isPreview` option is set
+
+## 2. Create RectangleDrawingPrimitive Plugin
+
+- [ ] 2.1 Create `src/plugins/rectangle-drawing.ts` implementing `ISeriesPrimitive<Time>` with renderer, pane view, and data model for two corner points `{time, price}`
+- [ ] 2.2 Implement `RectangleDrawingPaneRenderer.draw()` — filled semi-transparent rectangle with border, using `useBitmapCoordinateSpace` for HiDPI scaling
+- [ ] 2.3 Implement `hitTest(x, y)` — convert pixel to data coordinates, check if within rectangle time/price bounds
+- [ ] 2.4 Add `setSelected(isSelected)` and selection visual feedback (thicker border, increased opacity)
+- [ ] 2.5 Add preview mode support — dashed border and reduced opacity for preview rectangles during drawing
+- [ ] 2.6 Add `autoscaleInfo()` to include rectangle price range in chart scaling
+- [ ] 2.7 Set z-order to "bottom" so rectangles render behind candlesticks
+
+## 3. Wire Up Drawing Interaction in CandleChart
+
+- [ ] 3.1 Add state for drawing mode: `drawingState: {tool: 'line'|'rectangle', firstPoint: {time, price}} | null` and `previewPrimitive: TrendLine | RectangleDrawingPrimitive | null`
+- [ ] 3.2 Subscribe to `chart.subscribeClick()` — on first click when line/rectangle tool active, record first point and attach preview primitive; on second click, save annotation via API, detach preview, attach permanent primitive
+- [ ] 3.3 Subscribe to `chart.subscribeCrosshairMove()` — when drawing in progress, update preview primitive's endpoint via `updatePoints()` or equivalent
+- [ ] 3.4 Handle Escape key — detach preview primitive and clear drawing state
+- [ ] 3.5 Manage TrendLine primitives for saved line annotations — create/attach on load, detach on delete, update on edit
+
+## 4. Wire Up Rectangle Primitives in CandleChart
+
+- [ ] 4.1 On annotation fetch, create `RectangleDrawingPrimitive` instances for `label_type: "rectangle"` annotations and attach to series
+- [ ] 4.2 On chart switch, detach old rectangle primitives and create new ones for the new chart's annotations
+- [ ] 4.3 Handle rectangle selection — on click hit detected via primitive `hitTest()`, call `setSelected()` and track selected annotation ID
+- [ ] 4.4 Handle rectangle deletion — when delete tool active and hit detected, send DELETE API call, detach primitive, refresh annotations
+
+## 5. Update Toolbox
+
+- [ ] 5.1 Add "rectangle" tool button to Toolbox (using existing `RectangleHorizontal` lucide icon import, which is already present)
+- [ ] 5.2 Wire rectangle button to `onToolChange('rectangle')` with same toggle behavior as other tools
+
+## 6. Remove SVG Overlay
+
+- [ ] 6.1 Remove `SvgOverlay` import and JSX from `CandleChart.tsx`
+- [ ] 6.2 Delete `src/components/SvgOverlay.tsx`
+- [ ] 6.3 Move line annotation primitive management into CandleChart (replace what SvgOverlay was doing — loading saved lines, managing line primitives on annotation fetch/delete)
+
+## 7. Line Endpoint Dragging
+
+- [ ] 7.1 Implement drag detection — when a selected line's endpoint handle is clicked (via hitTest near endpoint), enter drag mode
+- [ ] 7.2 On crosshair move during drag, call `trendLine.updatePoints()` to reposition the dragged endpoint in real-time
+- [ ] 7.3 On click to release drag, persist updated geometry via PATCH /api/annotations/{id}
+
+## 8. Verification
+
+- [ ] 8.1 Verify existing saved line annotations render correctly with TrendLine plugin (visual parity with old SVG rendering)
+- [ ] 8.2 Verify line drawing, preview, selection, dragging, and deletion all work end-to-end
+- [ ] 8.3 Verify rectangle drawing, preview, selection, and deletion work end-to-end
+- [ ] 8.4 Verify chart zoom/pan correctly repositions both line and rectangle primitives
+- [ ] 8.5 Verify tool switching between line, rectangle, span, label, and delete modes works correctly
+- [ ] 8.6 Verify annotations persist and reload correctly on chart switch