The pure batch/reboot/stop state machine in WebConfigBatch.h was host-tested
but not referenced by production, so the real logic in WebConfigServer.cpp was
untested and the two could drift silently.
Repoint the production decision points at the spec: POST classification and
replay-state naming, drain pacing/all-ok/finish, reboot scheduling and firing,
result classification, confirm-reboot arming, and stop gating. MAX_BATCH and
STOP_WARN_MS now alias kMaxBatch/kStopWarnMs so the constants cannot drift.
Behavior-preserving. Two asymmetries are deliberate and documented in the
header: finishRebootAt()'s 0 return must not be assigned unconditionally
(the manual /api/reboot route also owns _reboot_at and could be cancelled),
and classifyPost() is consulted in two phases because the change count is
only known after parsing, which must not precede the Replay/Busy answer.
Native suite (14 suites) and both MQTT smoke builds green.