Combat: auto-play timed-out turn-based sessions to a real win/loss

A combat session abandoned past its 1h TTL is now resumed from persisted
mid-state and auto-played through the shared resolver to a real win or
loss, rather than flatly marked as a retreat. The bulk-UPDATE sweep is
replaced by listExpiredCombatSessions plus a reaper that locks the user,
auto-plays the fight, runs the normal close-out, and DMs the outcome.
markCombatSessionExpired remains the terminal fallback for sessions that
can't be reconstructed. Wired into eventTicker.

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

internal/plugin/combat_reaper.go

@@ -0,0 +1,98 @@
+package plugin
+
+import (
+	"fmt"
+	"log/slog"
+
+	"maunium.net/go/mautrix/id"
+)
+
+// Phase 13 — turn-based combat timeout reaper.
+//
+// A CombatSession expires 1h after its last action (combatSessionTTL). Per the
+// 2026-05-13 timeout decision, an abandoned fight is not flatly marked as a
+// retreat — the reaper resumes it from persisted mid-state and auto-plays the
+// rest of the fight through the same shared resolver a live !attack uses,
+// landing on a real win or loss. The player is DM'd the outcome.
+//
+// Sessions that cannot be reconstructed (zone run deleted, enemy no longer in
+// the bestiary) or that fail to converge within reaperRoundCap fall back to the
+// terminal 'expired' status with no fatal-blow side effects — see
+// markCombatSessionExpired.
+
+// reaperRoundCap bounds the auto-play loop. A turn-based round always lands at
+// least one damage roll eventually, so a real fight converges well within this;
+// the cap only guards against a pathological non-terminating session.
+const reaperRoundCap = 300
+
+// reapExpiredCombatSessions is the timeout reaper, driven off eventTicker (one
+// pass per minute). It auto-plays every stale session to a terminal status.
+func (p *AdventurePlugin) reapExpiredCombatSessions() {
+	expired, err := listExpiredCombatSessions()
+	if err != nil {
+		slog.Error("combat: reaper failed to list expired sessions", "err", err)
+		return
+	}
+	for _, sess := range expired {
+		p.reapCombatSession(sess.UserID, sess.SessionID)
+	}
+}
+
+// reapCombatSession auto-plays a single stale session under the player's lock.
+// It re-fetches the session after locking: the player may have finished the
+// fight in the window between listing and locking, in which case there is
+// nothing to do.
+func (p *AdventurePlugin) reapCombatSession(userIDStr, sessionID string) {
+	userID := id.UserID(userIDStr)
+	userMu := p.advUserLock(userID)
+	userMu.Lock()
+	defer userMu.Unlock()
+
+	sess, err := getActiveCombatSession(userID)
+	if err != nil {
+		slog.Error("combat: reaper failed to reload session", "user", userID, "err", err)
+		return
+	}
+	// Gone, replaced, or no longer the stale one — the player acted first.
+	if sess == nil || sess.SessionID != sessionID {
+		return
+	}
+
+	player, enemy, err := p.combatantsForSession(sess)
+	if err != nil {
+		// Can't reconstruct the fight — park it terminal so it isn't retried
+		// every minute forever.
+		slog.Warn("combat: reaper cannot rebuild session, marking expired",
+			"user", userID, "session", sess.SessionID, "err", err)
+		if merr := markCombatSessionExpired(sess.SessionID); merr != nil {
+			slog.Error("combat: reaper failed to mark session expired", "session", sess.SessionID, "err", merr)
+		}
+		return
+	}
+
+	rounds := 0
+	for sess.IsActive() {
+		if rounds >= reaperRoundCap {
+			slog.Warn("combat: reaper hit round cap, marking expired",
+				"user", userID, "session", sess.SessionID)
+			if merr := markCombatSessionExpired(sess.SessionID); merr != nil {
+				slog.Error("combat: reaper failed to mark session expired", "session", sess.SessionID, "err", merr)
+			}
+			return
+		}
+		if _, rerr := runCombatRound(sess, &player, &enemy, PlayerAction{Kind: ActionAttack}); rerr != nil {
+			slog.Error("combat: reaper round failed", "user", userID, "session", sess.SessionID, "err", rerr)
+			if merr := markCombatSessionExpired(sess.SessionID); merr != nil {
+				slog.Error("combat: reaper failed to mark session expired", "session", sess.SessionID, "err", merr)
+			}
+			return
+		}
+		rounds++
+	}
+
+	outcome := p.finishCombatSession(userID, sess, enemy)
+	preamble := fmt.Sprintf("⏳ Your fight with **%s** timed out — TwinBee finished it for you.\n\n", enemy.Name)
+	if err := p.SendDM(userID, preamble+outcome); err != nil {
+		slog.Error("combat: reaper failed to DM outcome", "user", userID, "err", err)
+	}
+}