fix: address 5 edge cases from review-work findings

- C3: include command args in auto-slash-command dedup key
- H2: track completed task summaries for ALL COMPLETE message
- H9: increment tmux close retry count on re-mark
- H8: detect stale MCP connections after disconnect+reconnect race
- H8: guard disconnectedSessions growth for non-MCP sessions
- C1: await tmux cleanup in plugin dispose lifecycle

src/features/tmux-subagent/tracked-session-state.ts

@@ -23,5 +23,6 @@ export function markTrackedSessionClosePending(tracked: TrackedSession): Tracked
   return {
     ...tracked,
     closePending: true,
+    closeRetryCount: tracked.closePending ? tracked.closeRetryCount + 1 : tracked.closeRetryCount,
   }
 }