N1/A4+A6: wire the stubbed milestone rewards, re-anchor mid-day events

A4 — the three "deferred to hookup" milestone grants now pay out:

  Long Game (T5 clear)   guaranteed Legendary via pickMagicItemForRarity
                         -> dropMagicItemLoot, rendered in a new
                         milestoneAward.Extra block.
  Survivalist (clean T3+) writes AdventureCharacter.Title and announces to
                         the games room. No schema bump — player_meta.title
                         already exists and saveAdvCharacter persists it.
  Two Weeks (day 15)     restocks 3 days of rations (clamped to Supplies.Max)
                         and grants 3 zone-tier consumables.

Two Weeks was specced as +5 max HP "via the expedition row". Dropped: combat
MaxHP comes from stats.HPBonus, built in combat_stats.go from gear/arena/
housing with no expedition in scope. Threading one through would leak an
expedition-only buff into the sim's balance corpus. A supply cache
self-expires with the run and needs no combat math.

A6 — mid-day events rolled 0.5%/player/day from a deferred ticker slot: one
sighting per ~200 days. The roll and its roll-minute scheduler are gone.
Events now fire where the player is demonstrably present and reading a DM:
the end-of-day digest (8%), a sale at Thom's (5%), and an arena cashout (5%),
capped at one event per player per UTC day. A player who hits all three lands
at ~1.19/week. tryTriggerEvent returns bool so a bail (dead / mid-fight /
event already active) hands the day's slot back rather than burning it.

The frequency test drives its own seeded PCG over the chance constants and
the daily cap, so it measures the policy and can't flake on global RNG order.

internal/plugin/adventure_events.go

@@ -23,18 +23,65 @@ type advActiveEvent struct {
 	ExpiresAt   time.Time
 }
 
-// ── In-memory schedule ───────────────────────────────────────────────────────
-// When a player acts on a given day, the next ticker iteration assigns them
-// a one-shot roll-minute 60–180 minutes in the future. At that minute, the
-// 0.5% trigger roll fires. Each player rolls at most once per UTC day.
+// ── Event anchors ────────────────────────────────────────────────────────────
+// N1/A6 — events used to roll at 0.5%/player/day from a deferred ticker slot,
+// which put one sighting in front of a daily player roughly every 200 days.
+// They now roll at moments the player is demonstrably present and reading a
+// DM: the end-of-day digest, a sale at Thom's, and an arena cashout. Each
+// player still sees at most one event per UTC day.
+//
+// The per-anchor chances below put a player who hits all three at ~1 event
+// per week; see TestAnchoredEventWeeklyRate.
+const (
+	advEventChanceDigest = 0.08
+	advEventChanceSell   = 0.05
+	advEventChanceArena  = 0.05
+)
 
 var (
-	advEventScheduleMu  sync.Mutex
-	advEventSchedule    map[string]int  // userID -> minute-of-day for the deferred roll
-	advEventRolled      map[string]bool // userID -> already rolled today
-	advEventScheduleDay string          // "2006-01-02" the maps belong to
+	advEventFiredMu  sync.Mutex
+	advEventFired    map[string]bool // userID -> an event already fired today
+	advEventFiredDay string          // "2006-01-02" the map belongs to
 )
 
+// claimDailyEventSlot reserves today's single event slot for `userID`.
+// Returns false when the player already had one fire today.
+func claimDailyEventSlot(userID id.UserID, day string) bool {
+	advEventFiredMu.Lock()
+	defer advEventFiredMu.Unlock()
+	if advEventFiredDay != day {
+		advEventFired = make(map[string]bool)
+		advEventFiredDay = day
+	}
+	if advEventFired[string(userID)] {
+		return false
+	}
+	advEventFired[string(userID)] = true
+	return true
+}
+
+// releaseDailyEventSlot hands the slot back when the trigger bailed before
+// anything reached the player, so a later anchor the same day can still fire.
+func releaseDailyEventSlot(userID id.UserID) {
+	advEventFiredMu.Lock()
+	defer advEventFiredMu.Unlock()
+	delete(advEventFired, string(userID))
+}
+
+// maybeFireAnchoredEvent rolls `chance` at one of the A6 anchor moments and,
+// on a hit, triggers the player's one mid-day event for today.
+func (p *AdventurePlugin) maybeFireAnchoredEvent(userID id.UserID, chance float64) {
+	if rand.Float64() >= chance {
+		return
+	}
+	if !claimDailyEventSlot(userID, time.Now().UTC().Format("2006-01-02")) {
+		return
+	}
+	if !p.tryTriggerEvent(userID) {
+		releaseDailyEventSlot(userID)
+	}
+}
+
 // ── Event Ticker ─────────────────────────────────────────────────────────────
 
 func (p *AdventurePlugin) eventTicker() {
@@ -46,90 +93,36 @@ func (p *AdventurePlugin) eventTicker() {
 		case <-p.stopCh:
 			return
 		case <-ticker.C:
-			now := time.Now().UTC()
-			dateKey := now.Format("2006-01-02")
-			currentMinute := now.Hour()*60 + now.Minute()
-
 			// Expire stale pending events every tick
 			expireAdvPendingEvents()
 
 			// Auto-play any combat sessions past their 1h timeout.
 			p.reapExpiredCombatSessions()
-
-			advEventScheduleMu.Lock()
-			if advEventScheduleDay != dateKey {
-				advEventSchedule = make(map[string]int)
-				advEventRolled = make(map[string]bool)
-				advEventScheduleDay = dateKey
-			}
-
-			// Schedule deferred rolls for any newly-acted players
-			chars, err := loadAllAdvCharacters()
-			if err != nil {
-				slog.Error("adventure: events: failed to load chars", "err", err)
-				advEventScheduleMu.Unlock()
-				continue
-			}
-			for _, c := range chars {
-				uid := string(c.UserID)
-				if !c.Alive || advEventRolled[uid] {
-					continue
-				}
-				if _, scheduled := advEventSchedule[uid]; scheduled {
-					continue
-				}
-				if !c.HasActedToday() {
-					continue
-				}
-				// Assign a one-shot roll 60–180 minutes from now, capped to 23:50 UTC.
-				rollMinute := currentMinute + 60 + rand.IntN(121)
-				if rollMinute > 23*60+50 {
-					rollMinute = 23*60 + 50
-				}
-				advEventSchedule[uid] = rollMinute
-				slog.Info("adventure: event roll scheduled", "user", uid, "minute", rollMinute)
-			}
-
-			// Find players whose roll-minute has arrived
-			var toRoll []id.UserID
-			for uid, minute := range advEventSchedule {
-				if minute <= currentMinute && !advEventRolled[uid] {
-					toRoll = append(toRoll, id.UserID(uid))
-					advEventRolled[uid] = true
-				}
-			}
-			advEventScheduleMu.Unlock()
-
-			for _, uid := range toRoll {
-				p.tryTriggerEvent(uid)
-			}
 		}
 	}
 }
 
-func (p *AdventurePlugin) tryTriggerEvent(userID id.UserID) {
-	// Load character — must be alive and have acted today
+// tryTriggerEvent fires the player's mid-day event. Reports whether an event
+// actually reached them — a false return means the caller's daily slot was
+// never spent. The trigger roll itself lives in maybeFireAnchoredEvent.
+func (p *AdventurePlugin) tryTriggerEvent(userID id.UserID) bool {
+	// Load character — must be alive.
 	char, err := loadAdvCharacter(userID)
-	if err != nil || char == nil || !char.Alive || !char.HasActedToday() {
-		return
+	if err != nil || char == nil || !char.Alive {
+		return false
 	}
 
 	// Already has an active event?
 	active, _ := loadAdvActiveEvent(userID)
 	if active != nil {
-		return
+		return false
 	}
 
 	// Mid-fight: a turn-based session locks the run. Don't drop a random
 	// overworld event into a live fight — the player can't act on it without
 	// finishing the fight first, and the trigger DM talks over the combat feed.
 	if hasActiveCombatSession(userID) {
-		return
-	}
-
-	// 0.5% chance
-	if rand.Float64() >= 0.005 {
-		return
+		return false
 	}
 
 	// Determine today's activity for filtering
@@ -138,7 +131,7 @@ func (p *AdventurePlugin) tryTriggerEvent(userID id.UserID) {
 	// Pick an event
 	event := advPickRandomEvent(userID, activityType)
 	if event == nil {
-		return
+		return false
 	}
 
 	// Insert into DB
@@ -147,7 +140,7 @@ func (p *AdventurePlugin) tryTriggerEvent(userID id.UserID) {
 	eventID, err := insertAdvEvent(userID, event.Key, expiresAt)
 	if err != nil {
 		slog.Error("adventure: events: failed to insert event", "user", userID, "err", err)
-		return
+		return false
 	}
 
 	slog.Info("adventure: mid-day event triggered", "user", userID, "event", event.Key, "id", eventID)
@@ -170,6 +163,7 @@ func (p *AdventurePlugin) tryTriggerEvent(userID id.UserID) {
 		})
 		_ = p.SendMessage(id.RoomID(gr), roomLine)
 	}
+	return true
 }
 
 // handleEventRespond processes `!adventure respond`.