Combat: guard daily-cron paths against mid-fight combat sessions

A turn-based elite/boss combat session locks the run for up to 1h and
can straddle any scheduled tick. Add hasActiveCombatSession() and consult
it from the morning DM, midnight idle reaper, expedition briefing/recap,
and mid-day random event paths so none of them fire DMs or mutate run
state into a live fight.

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

internal/plugin/combat_session.go

@@ -7,6 +7,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"log/slog"
 	"time"
 
 	"gogobee/internal/db"
@@ -256,6 +257,23 @@ func getActiveCombatSession(userID id.UserID) (*CombatSession, error) {
 	return s, err
 }
 
+// hasActiveCombatSession reports whether the player is currently locked into a
+// turn-based elite/boss fight. Daily-cron and periodic-ticker paths consult
+// this to avoid firing DMs or mutating run state into a live fight: an active
+// session locks the run (no `!zone advance`), so the player can't move it
+// forward and a cron path shouldn't either. The session carries a 1h TTL, so
+// the collision window is bounded — but real, since a fight can straddle any
+// scheduled tick. On a lookup error this returns false (fail-open): a missed
+// guard is a confusing DM, not corruption.
+func hasActiveCombatSession(userID id.UserID) bool {
+	s, err := getActiveCombatSession(userID)
+	if err != nil {
+		slog.Warn("combat: cron guard failed to check active session", "user", userID, "err", err)
+		return false
+	}
+	return s != nil
+}
+
 // getCombatSession fetches by ID regardless of status. Test/admin/reaper use.
 func getCombatSession(sessionID string) (*CombatSession, error) {
 	row := db.Get().QueryRow(`SELECT `+combatSessionCols+`