fix(tui): avoid startup cursor position query

Remove the redundant ratatui clear that waits for a cursor response.
Align login lifecycle and generated demo documentation with current behavior.

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

Author: echobt

scripts/render-demo-gif.sh

@@ -4,10 +4,13 @@
 # Two stages:
 #   1. generate_tui_demo paints the signed lock TUI (splash → typing → working)
 #      at 120×40 through cortex-tui.
-#   2. scripts/ansi-frames-to-gif.py rasterises those frames and calls ffmpeg.
+#   2. scripts/ansi-frames-to-gif.py rasterises those frames, composites a
+#      macOS-styled desktop and moving pointer, and calls ffmpeg.
 #
-# Requires: cargo, ffmpeg, python3 with Pillow.
-# Output size is 1232×912 with the default 16px font and 16px padding.
+# Requires: cargo, ffmpeg, python3 with Pillow, and a supported sans font
+# (Liberation Sans, DejaVu Sans, Noto Sans, or macOS Helvetica/Arial).
+# Raw raster: 1232×912 at the default 16px font and padding.
+# Composed GIF: 1416×1140. Validate with python3 scripts/check-macos-demo.py.
 
 set -euo pipefail
 

src/cortex-tui/src/runner/login_screen.rs

@@ -1,7 +1,7 @@
 //! Login Screen
 //!
-//! Inline TUI (no alternate screen) so the host shell prompt stays in
-//! scrollback above the picker.
+//! Uses the alternate screen by default. `run_with_options` follows the
+//! caller's terminal preferences; inline mode preserves scrollback.
 
 use std::path::{Path, PathBuf};
 use std::time::{Duration, Instant};

src/cortex-tui/src/runner/terminal.rs

@@ -279,12 +279,8 @@ impl CortexTerminal {
         // Own cleanup before the first fallible setup operation.
         init_terminal(&options)?;
         let backend = CrosstermBackend::new(stdout());
-        let mut terminal = Terminal::new(backend)?;
-        // Ratatui's initial diff assumes blank cells, even on the primary screen.
-        // Clear the visible viewport, not scrollback, before the first frame.
-        if options.clear_on_start {
-            terminal.clear()?;
-        }
+        // init_screen already clears when requested; Terminal::clear would query the cursor.
+        let terminal = Terminal::new(backend)?;
 
         Ok(Self {
             terminal,

src/cortex-tui/src/runner/terminal_tests.rs

@@ -8,12 +8,20 @@ fn startup_clears_visible_screen_in_both_modes() {
     assert!(startup.find("\x1b[?1049h").unwrap() < startup.find("\x1b[2J").unwrap());
     assert!(startup.contains("\x1b[0m\x1b[2J\x1b[1;1H"));
     assert!(!startup.contains("\x1b[3J"), "never erase scrollback");
+    assert!(
+        !startup.contains("\x1b[6n"),
+        "startup must not query the cursor"
+    );
 
     let mut output = Vec::new();
     init_screen(&mut output, &TerminalOptions::inline()).unwrap();
     let startup = String::from_utf8(output).unwrap();
     assert!(startup.contains("\x1b[0m\x1b[2J\x1b[1;1H"));
     assert!(!startup.contains("\x1b[3J"));
+    assert!(
+        !startup.contains("\x1b[6n"),
+        "startup must not query the cursor"
+    );
 }
 
 #[test]
@@ -53,7 +61,6 @@ fn inline_preflight_options_preserve_scrollback_without_switching_screens() {
         )
         .unwrap();
         let output = String::from_utf8(output).unwrap();
-        // CortexTerminal also clears the visible viewport after construction.
         // 2J is allowed; switching screens and purging history are not.
         for forbidden in ["\x1b[?1049h", "\x1b[?1049l", "\x1b[3J"] {
             assert!(!output.contains(forbidden), "unexpected {forbidden:?}");