docs(bf-4sdu): note that feature was already complete

notes/bf-4sdu.md

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+# BF-4SDU: Worker Memory Bar - Already Complete
+
+## Status: Feature Already Implemented
+
+The worker memory bar feature described in bead bf-4sdu was already fully implemented in commit `ea6e270` (2026-06-07 10:19:27 -0400).
+
+## Implementation Summary
+
+### Files Created/Modified:
+1. **`src/web/frontend/src/components/WorkerMemoryBar.tsx`** (new file, 141 lines)
+   - Proportional RSS memory bar (4 GB ceiling default, or per-worker limit if set)
+   - Peak RSS watermark marker (vertical white line)
+   - Text label showing current/limit (e.g., "1.2 GB / 4.0 GB")
+   - Swap indicator (🔁) if swap usage > 0
+   - Hides bar when `rssKb` is null
+
+2. **`src/web/frontend/src/types.ts`** (7 lines added)
+   - Added memory fields to `WorkerInfo`: `rssKb`, `peakRssKb`, `rssLimitBytes`, `rssPercent`, `swapKb`, `pid`
+
+3. **`src/web/frontend/src/components/WorkerGrid.tsx`** (8 lines added)
+   - Integrated `WorkerMemoryBar` component into each worker card
+
+## Verification
+
+The implementation matches all requirements:
+- ✅ RSS memory bar proportional to 4 GB ceiling (or per-worker limit)
+- ✅ Peak RSS watermark marker
+- ✅ Text label format: "X GB / Y GB"
+- ✅ Hides when `rssKb` is null
+
+## Action Taken
+
+No code changes needed. Documenting that feature is complete and closing bead.