fix: improve blocking read end-of-response detection

The original '>' detection was too broad and caught tool output lines.
Now we look for '> X: ' pattern (user prompt with speaker prefix) to
detect the start of a new user input, which marks the end of the
previous response.

poc-agent/src/observe.rs

@@ -128,11 +128,15 @@ pub async fn cmd_read_inner(follow: bool, block: bool, debug: bool) -> anyhow::R
                 print!("{}", line);
                 let _ = std::io::stdout().lock().flush();
                 
-                // In blocking mode, stop when we see a new user input (line starting with ">")
-                if block && line.trim_start().starts_with('>') {
+                // In blocking mode, stop when we see a new user input
+                // Format: "> X: " where X is a speaker (P, K, etc.)
+                if block && line.trim_start().starts_with("> ") {
+                    let after_gt = line.trim_start().strip_prefix("> ").unwrap_or("");
+                    if after_gt.contains(':') {
                         break;
                     }
                 }
+            }
             Err(_) => break,
         }
     }