docs(tb-67rg): investigate starvation alert - document false positive

The 8 'invisible' open beads were correctly filtered by br claim due to
unclosed blockers in a legitimate dependency chain.

Root blocker: tb-1me (in_progress, updated 12min ago, within 30min TTL)
- Directly blocks: tb-163k, tb-2ir, tb-2lh, tb-62m
- Indirectly blocks chain: tb-3iu → tb-5wj → tb-23i → tb-5n9

The claim SQL filters out beads with unclosed blockers (claim.rs lines 317-322).
This is correct behavior, not a configuration bug.

All blocked beads have 'split-child' label but the blocker filter is what
excludes them from claim eligibility, not the label itself.

Bead-Id: tb-67rg
Co-Authored-By: Claude <noreply@anthropic.com>

notes/tb-67rg-investigation.md

@@ -0,0 +1,65 @@
+# Investigation: Starvation Alert tb-67rg
+
+## Alert Summary
+**Date:** 2026-07-02
+**Alert:** "Beads invisible to worker" - 8 open beads but `br claim` returned `{}`
+
+## Root Cause: NOT a Bug - Legitimate Blocking Chain
+
+### Analysis
+The 8 "invisible" open beads were correctly filtered by `br claim` due to having **unclosed blockers**. This is the expected behavior per the claim SQL query in `bead-forge/src/claim.rs` (lines 317-322):
+
+```sql
+AND NOT EXISTS (
+    SELECT 1 FROM dependencies blocker_dep
+    INNER JOIN issues blocker ON blocker.id = blocker_dep.depends_on_id
+    WHERE blocker_dep.issue_id = i.id
+    AND blocker_dep.type IN ('blocks', 'parent-child', 'conditional-blocks', 'waits-for')
+    AND blocker.status != 'closed'
+)
+```
+
+### The Blocking Chain
+```
+tb-1me (in_progress, updated 12min ago)
+  ├─→ tb-163k (open, blocked by tb-1me)
+  ├─→ tb-2ir   (open, blocked by tb-1me)
+  ├─→ tb-2lh   (open, blocked by tb-1me)
+  ├─→ tb-62m   (open, blocked by tb-1me)
+  └─→ tb-2ir → tb-3iu → tb-5wj → tb-23i → tb-5n9
+       (chain of 5 more blocked beads)
+```
+
+**Root blocker:** `tb-1me` - "Run tmux detector acceptance tests and gather metrics"
+- Status: `in_progress`
+- Assignee: `claude-code-glm47-juliet`
+- Last updated: 2026-07-02 18:59:36 UTC (~12 minutes ago)
+- Claim TTL: 30 minutes (not stale yet)
+
+### All Open Beads Have Blockers
+
+| Bead ID | Title | Blocked By |
+|---------|-------|------------|
+| tb-163k | Analyze test results... | tb-1me |
+| tb-2ir | Record tmux detector viability... | tb-1me |
+| tb-2lh | Run first test iteration... | tb-1me |
+| tb-62m | Execute remaining test iterations... | tb-1me |
+| tb-3iu | Resolve Open question 1... | tb-2ir |
+| tb-5wj | Document production enablement... | tb-3iu |
+| tb-23i | Record tmux detector viability... | tb-5wj |
+| tb-5n9 | Prototype tmux-level fallback detector... | tb-23i |
+
+### Labels on Blocked Beads
+All blocked beads carry the `split-child` label, which indicates they were created from a parent/umbrella bead. This label does NOT affect claim eligibility - the blocker filter is what matters.
+
+## Conclusion
+
+**Status:** FALSE POSITIVE - No configuration error
+**Cause:** Legitimate dependency blocking, not a bug
+**Resolution:** Document the blocking chain behavior; update starvation detection to account for blocked beads
+
+## Recommendations
+
+1. **For Pluck/starvation detection:** When reporting "X open beads but none claimed," also check how many have unclosed blockers
+2. **For workflow:** The blocking chain is valid - wait for `tb-1me` to complete, then the chain will unblock sequentially
+3. **Documentation:** Add notes explaining that `split-child` beads with dependencies are filtered from claim queries