Why: Q1 WP4/WP6/WP7 - run persistence goes through a Store port
(FileStore carries the current layout), superstep boundaries write
tiered snapshots with a graph fingerprint for recovery continuity,
and the four hardcoded stop conditions move behind one Termination
registry with And/Or composition.
Evidence: go vet clean; full suite ok including new checkpoint,
continuity-rejection, termination-primitive, grant-cap and the
Q23-updated leader closeout tests; cmd module green with
SweepExpired wired into the sweeper loop.
Impact: runState saves via Store (FileStore unchanged by default);
advance writes sync/async/on_exit checkpoints and Resume rejects
graph-shape changes from the crash window; leader turn cap now
degrades through finalize instead of a bare failure (Q23); manual
repair grants are bounded (Q26); wakeup cap and step timeout read
from the same registry; the dead SweepExpired is now called (Q6).
Refs: Documents proposal 2026-10-07-agent-stack-n1q1i1-plans.md Q1 WP4/WP6/WP7
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