docs: add follow-up queue guide

docs/RECHECK-QUEUE.md

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+# Recheck Queue
+
+Open Problem Lab should have a visible queue for artifacts that are not wrong, but are not strong enough to remain load-bearing without another pass.
+
+## Purpose
+
+The recheck queue captures work that needs a second look because of weak evidence, old sources, unclear boundaries, reviewer concerns, field uncertainty, or changing context.
+
+It is a routing mechanism, not a rejection mechanism.
+
+## Queue entry
+
+```markdown
+## RQ-YYYY-NNN — Short name
+
+**Artifact:** Link to claim, evidence record, issue, PR, or problem-pack section.
+
+**Reason for recheck:** One paragraph.
+
+**Trigger:** Source age, field report, reviewer concern, dataset update, method concern, or status change.
+
+**Needed reviewer:** general | evidence | domain | quantitative | field | maintainer.
+
+**Smallest useful check:** The next action that would reduce uncertainty.
+
+**Decision after check:** keep | bound | dispute | archive | escalate.
+```
+
+## Reviewer guidance
+
+A reviewer should use the queue when work is promising but not ready to carry its current confidence level.
+
+## Agent guidance
+
+Agents should inspect the queue before proposing new work. A queued artifact is often the best place to make a valuable contribution.
+
+## Acceptance test
+
+A queue entry is useful when another contributor can immediately see what to check, why it matters, and how the result would change repository status.