feat(analytics): integrate analytics across remaining UI components

- Add slash command tracking:
  - Track command selection with method (click/keyboard/autocomplete)
  - Monitor command execution with parameters and timing
  - Record custom command creation events
- Enhance agent execution tracking:
  - Track agent lifecycle (start, progress, completion)
  - Monitor agent errors with retry context
  - Record execution duration and success metrics
- Add tab management analytics:
  - Track tab creation and closure events
  - Monitor active tab switches
- Implement timeline navigation tracking:
  - Track checkpoint navigation events
  - Monitor timeline interactions
- Update useAnalytics hook with comprehensive event helpers
- Export performance monitoring hooks from central index

This completes analytics integration across all major UI components
for full user interaction visibility.

src/components/TimelineNavigator.tsx

@@ -22,6 +22,7 @@ import { Label } from "@/components/ui/label";
 import { api, type Checkpoint, type TimelineNode, type SessionTimeline, type CheckpointDiff } from "@/lib/api";
 import { cn } from "@/lib/utils";
 import { formatDistanceToNow } from "date-fns";
+import { useTrackEvent } from "@/hooks";
 
 interface TimelineNavigatorProps {
   sessionId: string;
@@ -35,6 +36,10 @@ interface TimelineNavigatorProps {
    * are created elsewhere (e.g., auto-checkpoint after tool execution).
    */
   refreshVersion?: number;
+  /**
+   * Callback when a new checkpoint is created
+   */
+  onCheckpointCreated?: () => void;
   className?: string;
 }
 
@@ -49,6 +54,7 @@ export const TimelineNavigator: React.FC<TimelineNavigatorProps> = ({
   onCheckpointSelect,
   onFork,
   refreshVersion = 0,
+  onCheckpointCreated,
   className
 }) => {
   const [timeline, setTimeline] = useState<SessionTimeline | null>(null);
@@ -61,6 +67,9 @@ export const TimelineNavigator: React.FC<TimelineNavigatorProps> = ({
   const [error, setError] = useState<string | null>(null);
   const [diff, setDiff] = useState<CheckpointDiff | null>(null);
   const [compareCheckpoint, setCompareCheckpoint] = useState<Checkpoint | null>(null);
+  
+  // Analytics tracking
+  const trackEvent = useTrackEvent();
 
   // Load timeline on mount and whenever refreshVersion bumps
   useEffect(() => {
@@ -107,6 +116,8 @@ export const TimelineNavigator: React.FC<TimelineNavigatorProps> = ({
       setIsLoading(true);
       setError(null);
       
+      const sessionStartTime = Date.now(); // Using current time as we don't have session start time
+      
       await api.createCheckpoint(
         sessionId,
         projectId,
@@ -115,6 +126,18 @@ export const TimelineNavigator: React.FC<TimelineNavigatorProps> = ({
         checkpointDescription || undefined
       );
       
+      // Track checkpoint creation
+      const checkpointNumber = timeline ? timeline.totalCheckpoints + 1 : 1;
+      trackEvent.checkpointCreated({
+        checkpoint_number: checkpointNumber,
+        session_duration_at_checkpoint: Date.now() - sessionStartTime
+      });
+      
+      // Call parent callback if provided
+      if (onCheckpointCreated) {
+        onCheckpointCreated();
+      }
+      
       setCheckpointDescription("");
       setShowCreateDialog(false);
       await loadTimeline();
@@ -135,6 +158,9 @@ export const TimelineNavigator: React.FC<TimelineNavigatorProps> = ({
       setIsLoading(true);
       setError(null);
       
+      const checkpointTime = new Date(checkpoint.timestamp).getTime();
+      const timeSinceCheckpoint = Date.now() - checkpointTime;
+      
       // First create a checkpoint of current state
       await api.createCheckpoint(
         sessionId,
@@ -147,6 +173,12 @@ export const TimelineNavigator: React.FC<TimelineNavigatorProps> = ({
       // Then restore
       await api.restoreCheckpoint(checkpoint.id, sessionId, projectId, projectPath);
       
+      // Track checkpoint restoration
+      trackEvent.checkpointRestored({
+        checkpoint_id: checkpoint.id,
+        time_since_checkpoint_ms: timeSinceCheckpoint
+      });
+      
       await loadTimeline();
       onCheckpointSelect(checkpoint);
     } catch (err) {