fix(checkins): use systemEvent for cron triggers instead of agentTurn

Isolated agent sessions load plugins fresh with storage=null, causing
the tool factory to return null and no tools to be available. The agent
then outputs XML-like text instead of making proper tool calls.

Switch cron jobs to use systemEvent payload which runs in the main
gateway process where storage IS initialized. The message_received
hook already handles [system] checkins:trigger: and checkins:cleanup:
events.

extensions/checkins/src/cleanup.ts

@@ -59,6 +59,7 @@ export function buildCleanupCronJobs(storage: CheckinsStorage): CronJobCreate[]
   }
 
   // Build cleanup job for each timezone
+  // Use systemEvent to run in main gateway process (has access to initialized storage)
   const jobs: CronJobCreate[] = [];
   for (const tz of timezones) {
     jobs.push({
@@ -70,12 +71,11 @@ export function buildCleanupCronJobs(storage: CheckinsStorage): CronJobCreate[]
         expr: "5 0 * * *", // 00:05 (5 minutes past midnight per RESEARCH.md)
         tz,
       },
-      sessionTarget: "isolated",
+      sessionTarget: "main",
       wakeMode: "now",
       payload: {
-        kind: "agentTurn",
-        message: `[system] checkins:cleanup:${tz}`,
-        deliver: false,
+        kind: "systemEvent",
+        text: `[system] checkins:cleanup:${tz}`,
       },
     });
   }

extensions/checkins/src/scheduler.ts

@@ -32,17 +32,8 @@ export function getCheckInJobId(memberId: string): string {
  * @returns CronJobCreate configuration
  */
 export function buildCheckInCronJob(member: Member, team: Team): CronJobCreate {
-  // Build a clear instruction for the agent to call the trigger tool
-  const triggerMessage = [
-    "SCHEDULED CHECK-IN TRIGGER",
-    "",
-    "You must call the checkins_trigger tool with these exact parameters:",
-    `  memberId: "${member.id}"`,
-    `  teamId: "${team.id}"`,
-    "",
-    "Do not respond with any other message. Just call the tool.",
-  ].join("\n");
-
+  // Use systemEvent to trigger check-in via the main gateway process
+  // This avoids isolated agent sessions which don't have initialized plugin storage
   return {
     name: `Check-in: ${member.displayName ?? member.discordUserId}`,
     description: `Daily check-in for team ${team.name}`,
@@ -52,12 +43,12 @@ export function buildCheckInCronJob(member: Member, team: Team): CronJobCreate {
       expr: convertTimeToCronExpr(member.schedule.checkInTime),
       tz: member.schedule.timezone,
     },
-    sessionTarget: "isolated",
+    // sessionTarget is auto-set to "main" for systemEvent payloads
+    sessionTarget: "main",
     wakeMode: "now",
     payload: {
-      kind: "agentTurn",
-      message: triggerMessage,
-      deliver: false,
+      kind: "systemEvent",
+      text: `[system] checkins:trigger:${member.id}:${team.id}`,
     },
   };
 }