fix: read 200 tail lines to find preview through progress noise

Claude Code emits many progress lines during work, burying the last
assistant text. 5 lines was not enough to reach it.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

state.go

@@ -63,8 +63,8 @@ func DetectState(messages []JSONLMessage, now time.Time) SessionState {
 	return Unknown
 }
 
-// ExtractPreview finds the last assistant text content and returns the first
-// 5 lines, truncated to 300 characters.
+// ExtractPreview finds the last assistant text content and returns
+// the first 5 lines, truncated to 300 characters.
 func ExtractPreview(messages []JSONLMessage) string {
 	for i := len(messages) - 1; i >= 0; i-- {
 		msg := messages[i]