Camp: heal on pitch; ambient cooldown 3h → 6h

!camp now applies long-rest effects (HP, spell slots, exhaustion,
threat -5, Underforge heat) immediately instead of waiting for the
06:00 UTC briefing. New CampState.RestApplied flag stops
processOvernightCamp from re-applying at briefing — it just strikes
the camp.

Also dials ambient cooldown 3h → 6h so a workday gives ~1–2 hits
instead of ~3.

internal/plugin/dnd_expedition.go

@@ -53,6 +53,10 @@ type CampState struct {
 	RoomIndex     int       `json:"room_index"`
 	EstablishedAt time.Time `json:"established_at"`
 	NightEvents   []string  `json:"night_events"`
+	// RestApplied is set when the long-rest effects (HP refill, spell slots,
+	// 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"`
 }
 
 // ThreatEvent — §8.4.