umbrella: backlog relationship graph — the gaps the 2026-09-01 adoption exposed #15438

Adopting GitHub native sub-issues and dependencies (#15423, #15428) surfaced structural gaps in the backlog that the adoption itself does not close. Each child below is one of them, with the measurement that found it.

Live state after the adoption, read from the sub-issue and dependency APIs across 8,385 issues:
650 hierarchy links · 146 blocked_by edges · 72 parents · 59 of 78 umbrellas populated · max depth 3.

Tasks

• Ship the relationship tooling so a re-sweep is possible
• Label the 28 umbrellas that carry no umbrella label
• Attach the 555 open issues that sit outside the graph entirely
• Populate the 19 umbrellas that hold no children
• Consolidate the duplicated label taxonomy
• Resolve the 9 parent conflicts and nesting decisions
• Close out 6,314 unchecked acceptance criteria on closed issues
• Fix the branch-switch hook's git -C $VAR blind spot