fix bug where killed process linger in list

src/app.rs

@@ -292,20 +292,27 @@ impl App {
     }
 
     /// Confirm and execute a pending signal action.
-    pub fn confirm_signal(&mut self, sender: &mut dyn FnMut(i32, Signal) -> Result<(), String>) {
-        let Some(pending) = self.pending_confirmation.take() else {
-            return;
-        };
+    ///
+    /// Returns `Some(pid)` when the sender accepted the signal so callers can
+    /// follow up (e.g. wait for the kernel to remove the entry from `/proc`).
+    /// Returns `None` when no confirmation was pending or the sender failed.
+    pub fn confirm_signal(
+        &mut self,
+        sender: &mut dyn FnMut(i32, Signal) -> Result<(), String>,
+    ) -> Option<i32> {
+        let pending = self.pending_confirmation.take()?;
 
         match sender(pending.pid, pending.signal) {
             Ok(()) => {
                 self.status = format!(
                     "sent {:?} ({}) to pid {}",
                     pending.signal, pending.digit, pending.pid
                 );
+                Some(pending.pid)
             }
             Err(err) => {
                 self.status = format!("failed to signal pid {}: {}", pending.pid, err);
+                None
             }
         }
     }

src/debug_tui.rs

@@ -57,6 +57,7 @@ pub(crate) fn run() -> Result<()> {
         build_debug_rows(seed.get())
     };
     let mut sender = debug_signal_sender;
+    let mut await_pid_gone = |_pid: i32| {};
     let mut app = App::with_rows(None, initial_rows);
     app.status = "debug tui: synthetic rows only".to_string();
     let result = run_event_loop(
@@ -65,6 +66,7 @@ pub(crate) fn run() -> Result<()> {
         &mut next_event,
         &mut refresh_rows,
         &mut sender,
+        &mut await_pid_gone,
     );
     restore_terminal(terminal);
     result