Splits the legacy briefing body into nightRolloverBurn + nightRolloverDrift,
plus a processNightCamp convenience. For expeditions started after the new
eventAnchoredCutoff, the 06:00 UTC briefing stops mutating: it posts a
re-engagement DM, and only force-fires processNightCamp itself after a 28h
safety-net window. Day++/burn/threat-drift now ride along the autopilot
night-camp pitch (decideAutopilotCamp sets Night=true when ≥16h since the
last rollover) and on the first player !camp since the last rollover. The
legacy UTC-anchored flow still works via the same staged helpers, with
processOvernightCamp interleaved to preserve the rest-before-drift ordering.
Tests pin eventAnchoredCutoff to year 9999 in TestMain so the existing
legacy assertions still run; new tests cover the night decision, the
night-camp pitch advancing the day, the event-anchored skip, and the
safety-net force-rollover.
New expedition_autocamp.go: pure decideAutopilotCamp + pitchAutopilotCamp
+ dwell-window lifecycle. Wired into tryAutoRun so the background ticker
pitches a rest camp on low HP and a base-camp waypoint on region-boss
clear; auto-pitched camps last minAutoCampDwell (4h) before the next tick
breaks them and walks. CampState.AutoPitched separates auto- vs player-
pitched camp lifetimes so a player !camp stays sticky.
Day-rollover semantics unchanged — still UTC-anchored; D2-b moves
day++/burn/threat-drift onto the camp-pitch event.
