daily-fix: catch task lifecycle commits stranded off main at

Overview / Motivation

Auto-filed by /daily 2026-07-06 (route 2: behavior/logic change -> independent review), from the nightly transcript problem sweep.

Goal

Add a post-transition landing check (after a lifecycle mutation commits, verify the commit is reachable from main / warn loudly if not) or a periodic task.py audit alert cron that surfaces stranded lifecycle commits at creation time, not at the next drift repair. Secondary (lower value, same incident): a verifier warning for plans that stage whole task dirs with untracked residue.

Workflow gap

• Bug observed: The 15-problem tasks/REGISTRY.json drift repaired by #1083 (session de296c4a, 2026-07-06) traced to task.py lifecycle commits stranded on never-merged issue- branches; no preventive guard exists, so drift is only caught at the next manual audit/repair. #1083's session parked this prevention candidate under the recursion guard.
• Why it is a workflow gap: the failure originates in the workflow surface / shared helper named below, not in any one experiment.
• Confidence (emitter): medium

Scope / surfaces

• Primary target: scripts/task.py
• Grep the workflow surface for the pattern before editing and update every hit; list them in the plan.

Constraints / invariants

• scripts/workflow_lint.py --check-asks + --check-references stay green; ruff clean on touched files; relevant tests pass.

Provenance

• workflow_fix_target: scripts/task.py
• source: /daily 2026-07-06 problem sweep (transcript-mined)