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

packages/mosaic/src/commands/fleet.spec.ts

@@ -855,7 +855,7 @@ describe('fleet ps — command construction', () => {
       '-t',
       '=canary-pi: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}',
     ]);
   });
 
@@ -1079,9 +1079,11 @@ describe('fleet ps — systemd show parsing', () => {
 describe('fleet ps — tmux list-panes parsing', () => {
   const NOW_MS = 1_700_000_000_000;
 
-  it('parses alive pane with pid, command, and idle time', () => {
-    const activityEpoch = Math.floor((NOW_MS - 30_000) / 1000); // 30s ago
-    const output = `12345 claude 0 ${activityEpoch}\n`;
+  it('uses pane_activity when present', () => {
+    const paneActivityEpoch = Math.floor((NOW_MS - 30_000) / 1000); // 30s ago
+    const windowActivityEpoch = Math.floor((NOW_MS - 60_000) / 1000); // 60s ago
+    const sessionActivityEpoch = Math.floor((NOW_MS - 90_000) / 1000); // 90s ago
+    const output = `12345 claude 0 ${paneActivityEpoch} ${windowActivityEpoch} ${sessionActivityEpoch}\n`;
     const result = parseTmuxListPanes(output, NOW_MS);
     expect(result.pid).toBe(12345);
     expect(result.command).toBe('claude');
@@ -1089,8 +1091,45 @@ describe('fleet ps — tmux list-panes parsing', () => {
     expect(result.idleSeconds).toBe(30);
   });
 
+  it('uses window_activity when pane_activity is empty', () => {
+    const windowActivityEpoch = Math.floor((NOW_MS - 45_000) / 1000); // 45s ago
+    const sessionActivityEpoch = Math.floor((NOW_MS - 90_000) / 1000); // 90s ago
+    const output = `12345 node 0  ${windowActivityEpoch} ${sessionActivityEpoch}\n`;
+    expect(output).toContain('0  '); // empty pane_activity preserves index alignment
+    const result = parseTmuxListPanes(output, NOW_MS);
+    expect(result.pid).toBe(12345);
+    expect(result.command).toBe('node');
+    expect(result.dead).toBe(false);
+    expect(result.idleSeconds).toBe(45);
+  });
+
+  it('uses session_activity when pane_activity and window_activity are empty', () => {
+    const sessionActivityEpoch = Math.floor((NOW_MS - 75_000) / 1000); // 75s ago
+    const output = `12345 node 0   ${sessionActivityEpoch}\n`;
+    const result = parseTmuxListPanes(output, NOW_MS);
+    expect(result.idleSeconds).toBe(75);
+  });
+
+  it('reports null idleSeconds when all activity sources are empty', () => {
+    const output = '12345 node 0   \n';
+    const result = parseTmuxListPanes(output, NOW_MS);
+    expect(result.idleSeconds).toBeNull();
+  });
+
+  it('computes exact idle seconds from now minus epoch seconds', () => {
+    const activityEpoch = 1_699_999_877;
+    const result = parseTmuxListPanes(`12345 claude 0 ${activityEpoch} 0 0\n`, NOW_MS);
+    expect(result.idleSeconds).toBe(123);
+  });
+
+  it('clamps future activity epochs to 0 idle seconds', () => {
+    const futureActivityEpoch = Math.floor((NOW_MS + 30_000) / 1000);
+    const result = parseTmuxListPanes(`12345 claude 0 ${futureActivityEpoch} 0 0\n`, NOW_MS);
+    expect(result.idleSeconds).toBe(0);
+  });
+
   it('reports dead pane when pane_dead=1', () => {
-    const output = `0 bash 1 0\n`;
+    const output = `0 bash 1 0 0 0\n`;
     const result = parseTmuxListPanes(output, NOW_MS);
     expect(result.dead).toBe(true);
   });