docs(tb-bctb): document starvation alert investigation - false alarm

All 10 open beads have special labels (deferred, split-child) that
filter them from bf claim. System working as designed.

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

notes/tb-bctb.md

@@ -0,0 +1,57 @@
+# Bead Worker Starvation Alert - tb-bctb
+
+## Issue
+Open beads existed but Pluck (bead-worker) found none - appeared to be a configuration error.
+
+## Investigation Summary
+
+### Bead Count
+- **Total beads**: 45
+- **Open**: 10
+- **In-progress**: 0
+- **Actually claimable**: 0
+
+### Root Cause
+All 10 open beads have special labels that exclude them from `bf claim`:
+
+**With `deferred` label (3 beads):**
+- `tb-1me`: "Run tmux detector acceptance tests and gather metrics" (deferred, umbrella)
+- `tb-23i`: "Record tmux detector viability verdict and resolve plan Open question 1" (deferred, split-child, umbrella)
+- `tb-5n9`: "Prototype tmux-level fallback detector to validate the harness-agnostic adapter seam" (deferred, umbrella)
+
+**With `split-child` label only (7 beads):**
+- `tb-163k`: "Analyze test results and document findings in decisions.md"
+- `tb-1p2a`: "Document findings in decisions.md"
+- `tb-2ir`: "Record tmux detector viability verdict in decisions.md"
+- `tb-2lh`: "Run first test iteration and establish measurement baseline"
+- `tb-3iu`: "Resolve Open question 1 in plan.md"
+- `tb-5wj`: "Document production enablement or alternatives for tmux detector"
+- `tb-62m`: "Execute remaining test iterations (runs 2-5)"
+
+### Design Behavior
+
+The `bf claim` command (bead-forge) internally filters beads with these labels:
+- **`deferred`** - Beads that should be worked on later
+- **`split-child`** - Sub-tasks that should be claimed together with their parent umbrella bead
+- **`umbrella`** - Parent beads that manage their own children
+
+This is **working as designed**, not a configuration error.
+
+### Verification
+
+```bash
+$ bf claim --assignee "test-worker" --dry-run
+No beads available to claim
+```
+
+## Resolution
+
+**False alarm** - The starvation alert was triggered because the monitoring system saw open beads but didn't account for label-based filtering. The bead-worker system correctly identified that there are 0 beads available to claim after applying the intended filters.
+
+## Recommendations
+
+1. **Update starvation detection** - Future alerts should check `bf claim --dry-run` output instead of just counting open beads
+2. **Label documentation** - Ensure the bead-worker documentation clearly explains which labels cause beads to be filtered
+3. **Monitoring improvement** - The alert should distinguish between:
+   - **Actual starvation** (beads exist but can't be claimed due to a bug)
+   - **Expected filtering** (all open beads have special labels and shouldn't be claimed)