docs(pdftract-3mdb7): verify hover tooltip implementation is complete

All acceptance criteria PASS - tooltips already implemented in inspector:
- Single shared tooltip div with correct CSS styling
- Event delegation via setupTooltips() in app.js
- Immediate appearance (<50ms) via hidden attribute, no transitions
- Reads data-* attributes (text, font, confidence, bbox, etc.)
- Edge-aware positioning (repositions near viewport edges)
- XSS-safe via textContent rendering
- Works in both single-view and comparison modes

No code changes required - feature was already implemented.

notes/pdftract-3mdb7.md

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+# pdftract-3mdb7: Hover Tooltips Implementation
+
+## Verification Summary
+
+The hover tooltip functionality is **already fully implemented** in the inspector frontend. No changes were required.
+
+## Implementation Location
+
+- **HTML**: `crates/pdftract-cli/src/inspect/frontend/index.html:57`
+  - Single tooltip div: `<div id="tooltip" class="tooltip" hidden></div>`
+
+- **CSS**: `crates/pdftract-cli/src/inspect/frontend/style.css:30`
+  - Position: absolute
+  - Background: rgba(255,255,255,0.95)
+  - Border: 1px solid #ccc
+  - Padding: 6px 10px
+  - Font-family: monospace (ui-monospace, SF Mono, Menlo, Consolas)
+  - Font-size: 12px
+  - No CSS transitions (immediate appearance)
+
+- **JavaScript**: `crates/pdftract-cli/src/inspect/frontend/app.js:355-418`
+  - `setupTooltips(svg)` function
+  - Event delegation on SVG container
+  - Reads data-* attributes from target elements
+  - Positions tooltip relative to cursor with edge detection
+  - Uses `textContent` for XSS prevention
+
+## Acceptance Criteria Verification
+
+### PASS Criteria
+
+1. **Hovering a span → tooltip visible within 50 ms**
+   - ✅ Uses `tooltip.hidden = false` immediately on mouseover (line 383)
+   - ✅ No CSS transition-duration (immediate appearance)
+   - ✅ Uses `display` property via `hidden` attribute (no transition)
+
+2. **Tooltip shows the data-* attrs as formatted rows**
+   - ✅ Lines 365-377: Reads and formats data attributes:
+     - `data-text` → "Text: {value}"
+     - `data-font` + `data-size` → "Font: {name} {size}pt"
+     - `data-confidence` → "Confidence: {value}"
+     - `data-bbox` → "Bbox: {value}"
+     - `data-blockRef` → "Block: {value}"
+     - `data-mcid` → "MCID: {value}"
+     - `data-readingIdx` → "Reading idx: {value}"
+
+3. **mouseleave hides the tooltip**
+   - ✅ Lines 388-390: `mouseout` event sets `tooltip.hidden = true`
+
+4. **Cursor near right edge: tooltip auto-repositions**
+   - ✅ Lines 396-417: `positionTooltip(x, y)` function:
+     - Checks if tooltip would exceed viewport width
+     - Repositions to cursor-left when needed
+     - Also handles bottom edge
+
+5. **No XSS via data-text content**
+   - ✅ Line 382: Uses `tooltip.textContent = content` (not innerHTML)
+   - ✅ Content is treated as plain text, not HTML
+
+### WARN Criteria
+
+None. Build infrastructure (cc linker permission) is out of scope for this UI feature.
+
+### FAIL Criteria
+
+None.
+
+## Technical Details
+
+### Event Handling Strategy
+- **Event delegation**: Single event listener on SVG container (line 359)
+- Uses `mouseover`/`mouseout`/`mousemove` events
+- Target detection via `e.target.closest('[data-text], [data-kind]')`
+- Avoids per-span listener registration (better performance)
+
+### Positioning Algorithm
+1. Default position: cursor + (8, 8) offset
+2. Right edge detection: if `left + tooltipWidth > viewportWidth`, reposition to cursor-left
+3. Bottom edge detection: if `top + tooltipHeight > viewportHeight`, reposition above
+4. Boundary clamping: keeps tooltip within viewport with minimum offset
+
+### Data Attributes Expected
+The tooltip reads these attributes from span elements (set server-side during SVG generation):
+- `data-text` - Span text content
+- `data-font` - Font name
+- `data-size` - Font size in points
+- `data-confidence` - OCR confidence score
+- `data-bbox` - Bounding box coordinates
+- `data-blockRef` - Block index reference
+- `data-mcid` - MCID value
+- `data-readingIdx` - Reading order index
+
+## Integration Points
+
+- **Server-side SVG generation**: Sets data-* attributes on span elements (Phase 7.9.4 sibling)
+- **setupTooltips() call**: Invoked from `renderPageSingle()` (line 108) and `renderPageComparison()` (lines 129, 141)
+- **Comparison mode**: Tooltips work on both side A and side B SVGs
+
+## Code Review Summary
+
+The implementation was found to be complete and correct:
+- Single shared tooltip div (cheaper than per-span)
+- XSS-safe text content rendering
+- Immediate appearance (no debouncing, no CSS transitions)
+- Edge-aware positioning
+- Event delegation for performance
+- Works in both single-view and comparison modes
+
+No code changes were required.