docs(bf-48nk): add retrospective notes - all gaps already implemented

The bead description claimed significant implementation gaps, but upon
investigation all mentioned features were already complete:

- memoryProfiler.ts: exists (f824c2e)
- FileHeatmap treemap/timelapse: fully implemented
- SpanDag zoom/pan: fully implemented
- Only 1 test failing (selector bug, now fixed)

All tests pass: 2399 passed, 4 skipped (65 test files)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

notes/bf-48nk.md

@@ -0,0 +1,48 @@
+# Bead bf-48nk: FABRIC Implementation Gap Closure
+
+## Status: Already Complete - Test Fix Only
+
+The bead description claimed significant implementation gaps in FABRIC, but upon investigation all mentioned features were already fully implemented. This was a retrospective bead for work already complete.
+
+## What Was Found
+
+### Claimed Gaps (All Already Implemented)
+
+1. **Missing module: src/memoryProfiler.ts**
+   - **Reality**: File exists and is fully implemented (7530 bytes)
+   - Already completed in commit f824c2e on 2026-05-02
+   - See notes/bf-5r8a.md for full details
+
+2. **Web frontend: treemap + timelapse in FileHeatmap not implemented**
+   - **Reality**: Both features fully implemented in src/web/frontend/src/components/FileHeatmap.tsx
+   - Treemap view: lines 443-524 (calculateTreemapLayout function)
+   - Timelapse view: lines 526-641 (playback controls, speed, slider, loop)
+
+3. **Web frontend: SpanDag zoom/pan interaction not implemented**
+   - **Reality**: Fully implemented in src/web/frontend/src/components/SpanDag.tsx
+   - Zoom controls: lines 231-259
+   - Pan functionality: lines 180-206
+   - All 13 SpanDag zoom/pan tests passing
+
+4. **Bug fixes: 89 failing unit tests**
+   - **Reality**: Only 1 failing test out of 2403 total
+   - The failure was a test selector bug, not implementation gap
+
+## Actual Work Done
+
+Fixed one failing test:
+- **File**: src/web/frontend/test/FileHeatmap.test.tsx
+- **Issue**: Test selector `.timelapse-playback button.primary` expected button to have "primary" class
+- **Fix**: Changed to `.timelapse-playback button` to find button regardless of play state
+- **Root cause**: Button only has "primary" class when isPlaying=true, initially false
+
+## Final Test Results
+
+- 65 test files passed
+- 2399 tests passed
+- 4 skipped
+- 0 failed
+
+## Conclusion
+
+The genesis bead description was based on outdated information. All claimed implementation gaps were already complete. The only actionable item was a single test selector bug which has been fixed.