The 2026-08-20 livelock ran 21h with no page. TidalDBClusterReseedPending is
`tidaldb_cluster_reseed_required == 1 for 10m`, written for exactly this, but the
defect cleared the marker ~200ms after each latch, so the gauge flapped 1->0
every ~30s and never held 1 for 10m. Add TidalDBClusterReseedFlapping, which
keys off `changes(...[15m]) > 2` instead of a hold duration, so a latch/clear
loop pages even when the gauge reads 0 at both ends of the window and even if a
future clear path reintroduces the spurious clear.
Also add an on-call banner for the operator intervention now in force: the
client Service selector is narrowed to keep tidaldb-0 out of the read path,
because its shard-1 frontier was cross-seeded from shard 2's snapshot artifact
and its reads are untrustworthy even at lag_events: 0. The banner carries the
footgun (the label is on the pods, not the template, so it does not survive pod
recreation) plus repair and revert commands.
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