Adv 2.0 D&D Phase 12 E2a: Threat Clock state machine

Threshold model on top of the E1a persistence: ThreatBand bracketing
(Quiet/Stirring/Alert/Hostile/Siege) with per-band combat/supply/rest
knobs (ThreatBandInfo). Daily threat drift (+3/day, GMMood-modded:
effusive→-3 elated, hostile→+5 wrathful) wired into the 06:00 briefing
rollover; no-op once the boss is down.

Threshold crossings emit a flavor-bearing log entry pulling from the
prewritten flavor.ThreatClock{Stirring,Alert,Hostile,Siege} pools.
applyBossDefeatThreat is the -20 hook for the eventual combat-completion
wiring (combat→expedition link is a later phase).

Combat-driven modifiers (loud-ability, escape, combat-in-new-room) are
deferred to the same combat-link phase since expeditions don't currently
host their own combat path.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/plugin/dnd_expedition_cycle.go

@@ -162,6 +162,12 @@ func (p *AdventurePlugin) deliverBriefing(e *Expedition, now time.Time) error {
 	e.Supplies = newSupplies
 	e.CurrentDay++
 
+	// E2a: daily threat drift (+3 base, GM-mood modifier). No-op after
+	// boss kill. May cross a threshold and append a flavor-bearing log.
+	if _, _, err := applyDailyThreatDrift(e); err != nil {
+		slog.Warn("expedition: threat drift", "expedition", e.ID, "err", err)
+	}
+
 	line := pickMorningBriefing(e.CurrentDay)
 	body := renderMorningBriefing(e, line, burn)