Style the input cursor yellow underline in safe mode

Author: alexylon

CHANGELOG.md

@@ -33,7 +33,7 @@ All notable changes to Sofos are documented in this file.
 - **A panicking worker no longer prints a zeroed session summary.** The shutdown path now carries an explicit `panicked` flag so the goodbye line is preceded by a "Session ended unexpectedly" warning instead of pretending the run finished cleanly with no usage at all.
 
 - **`Ctrl+C` while the slash-command popup is open dismisses the popup.** It used to fall through to the outer handler and quit the session, which surprised users who only wanted to bail out of the suggestion list. Ctrl+C with the popup closed still requests shutdown.
-- **The cursor shape now follows the active mode after `/safe` and `/normal`.** Toggling safe mode mid-session previously updated the status line but left the cursor in its old shape; the cursor now switches to the safe-mode underscore on `/safe` and back to the default block on `/normal`, matching the startup behaviour.
+- **The input cursor now follows the active mode after `/safe` and `/normal`.** Safe mode draws the cursor as a yellow underline inside the input box (matching the yellow `safe` status indicator); normal mode keeps the default reversed block. Toggling mid-session updates the cursor immediately, matching the startup behaviour.
 - **A panic anywhere inside the TUI now restores the terminal before the backtrace prints.** A process-wide panic hook disables raw mode, disables bracketed paste, pops the keyboard enhancement flags, and shows the cursor through a real-tty handle that bypasses the output-capture pipe — so even a panic that strikes before the local Drop chain runs leaves the user with a usable shell.
 - **Quitting while a confirmation modal is on screen no longer hangs the worker.** The event loop now sends the modal's default answer back before tearing down, unblocking the worker thread that was parked waiting for a reply so the `join` on shutdown completes promptly.
 - **Tool output without newlines no longer freezes the UI.** A captured pipe that delivered a multi-kilobyte blob with no `\n` used to keep the reader thread waiting silently; sofos now flushes the partial line to the UI every 4 KB and continues reading.

src/repl/tui/ui.rs

@@ -195,6 +195,16 @@ fn draw_input(frame: &mut Frame, area: Rect, app: &App) {
     }
     let title = Line::from(title_spans);
 
+    // Yellow underline in safe mode, default reversed block otherwise.
+    if safe {
+        textarea.set_cursor_style(
+            Style::default()
+                .fg(SAFE_MODE_FG)
+                .add_modifier(Modifier::UNDERLINED),
+        );
+    } else {
+        textarea.set_cursor_style(Style::default().add_modifier(Modifier::REVERSED));
+    }
     textarea.set_block(
         Block::default()
             .borders(Borders::ALL)