Long expeditions D2-a: autopilot camp scheduler

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.

internal/plugin/dnd_expedition.go

@@ -57,6 +57,11 @@ type CampState struct {
 	// threat -5 etc.) have already been applied at pitch time. processOvernightCamp
 	// uses it to skip re-applying so the night cycle just breaks the camp.
 	RestApplied bool `json:"rest_applied,omitempty"`
+	// AutoPitched is set when the long-expedition autopilot pitched this
+	// camp. The autorun ticker breaks an auto-pitched camp itself after a
+	// minimum dwell so the walk can keep moving; player-pitched camps stay
+	// up until the player breaks them (or moves on).
+	AutoPitched bool `json:"auto_pitched,omitempty"`
 }
 
 // ThreatEvent — §8.4.