fix(fleet): derive pane idle from window activity fallback (#651)

packages/mosaic/src/commands/fleet.ts

@@ -524,7 +524,7 @@ export function buildSystemdShowCommand(agentName: string): string[] {
 
 /**
  * Returns the tmux list-panes command for an agent pane.
- * Format: `#{pane_pid} #{pane_current_command} #{pane_dead} #{pane_activity}`
+ * Format: `#{pane_pid} #{pane_current_command} #{pane_dead} #{pane_activity} #{window_activity} #{session_activity}`
  */
 export function buildTmuxListPanesCommand(agentName: string, socketName = ''): string[] {
   return [
@@ -534,7 +534,7 @@ export function buildTmuxListPanesCommand(agentName: string, socketName = ''): s
     '-t',
     `=${agentName}:0.0`,
     '-F',
-    '#{pane_pid} #{pane_current_command} #{pane_dead} #{pane_activity}',
+    '#{pane_pid} #{pane_current_command} #{pane_dead} #{pane_activity} #{window_activity} #{session_activity}',
   ];
 }
 
@@ -634,8 +634,8 @@ export function parseSystemdShow(output: string): {
 }
 
 /**
- * Parse the output of `tmux list-panes -F '#{pane_pid} #{pane_current_command} #{pane_dead} #{pane_activity}'`
- * pane_activity is a Unix epoch timestamp (seconds).
+ * Parse the output of `tmux list-panes -F '#{pane_pid} #{pane_current_command} #{pane_dead} #{pane_activity} #{window_activity} #{session_activity}'`
+ * Activity fields are Unix epoch timestamps (seconds), ordered most precise to coarsest.
  */
 export function parseTmuxListPanes(
   output: string,
@@ -645,16 +645,18 @@ export function parseTmuxListPanes(
   if (!line) {
     return { pid: null, command: null, dead: true, idleSeconds: null };
   }
-  // format: <pid> <command> <dead(0|1)> <activity_epoch>
+  // format: <pid> <command> <dead(0|1)> <pane_activity> <window_activity> <session_activity>
   const parts = line.split(' ');
   const pid = parts[0] ? (Number.isFinite(Number(parts[0])) ? Number(parts[0]) : null) : null;
   const command = parts[1] ?? null;
   const dead = parts[2] === '1';
-  const activityEpoch = parts[3] ? Number(parts[3]) : NaN;
-  const idleSeconds =
-    Number.isFinite(activityEpoch) && activityEpoch > 0
-      ? Math.floor((nowMs - activityEpoch * 1000) / 1000)
-      : null;
+  const activityEpoch = parts
+    .slice(3, 6)
+    .map((part) => (part ? Number(part) : NaN))
+    .find((epoch) => Number.isFinite(epoch) && epoch > 0);
+  const idleSeconds = activityEpoch
+    ? Math.max(0, Math.floor((nowMs - activityEpoch * 1000) / 1000))
+    : null;
   return { pid, command, dead, idleSeconds };
 }