feat(ratelimit): persist window token counters across restarts

Save window state (resets_at + token counts) to ~/.claude/ on shutdown
and every poll cycle. On startup, restore counters if the window hasn't
rolled over. Fixes token counters resetting to zero on deploy.

internal/ratelimit/tracker.go

@@ -45,14 +45,16 @@ func NewTracker(tokenFn func() string) *Tracker {
 // Start begins the background poll loop.
 func (t *Tracker) Start(ctx context.Context) {
 	go func() {
-		// Poll immediately on start
 		t.poll(ctx)
+		t.Restore()
 		for {
 			select {
 			case <-ctx.Done():
+				t.Save()
 				return
 			case <-time.After(5 * time.Minute):
 				t.poll(ctx)
+				t.Save()
 			}
 		}
 	}()