fix(input): honor auxiliary-window key gate

Both original key handlers return without processing gameplay keys while any of
the four child-window slots is occupied. Rust continued to toggle sound through
Help, HighScore, and name-entry UI and used F1 to close Help, behavior the main
Win16 window cannot perform through an active child.

Limit recovered F1 and F12 handling to the attract and playing screens. The
portable Enter/Escape Help return remains available as an explicit modern
control without bypassing the original main-window gate.

Test Plan:
- `cargo test --workspace --all-targets --all-features` -- 125 passed
- `cargo clippy --workspace --all-targets --all-features -- -D warnings` -- passed
- `rumdl check --flavor commonmark RECONSTRUCTION.md CHANGELOG.md` -- passed
- `git diff --cached --check` -- passed

tdkpin-rs/src/app.rs

@@ -285,16 +285,13 @@ impl App {
     }
 
     fn handle_global_input(&mut self) {
-        if is_key_released(KeyCode::F12) {
+        let base_screen = matches!(self.screen, Screen::Attract | Screen::Playing);
+        if base_screen && is_key_released(KeyCode::F12) {
             self.sounds_enabled = !self.sounds_enabled;
         }
-        if is_key_pressed(KeyCode::F1) && self.screen != Screen::NameEntry {
-            if self.screen == Screen::Help {
-                self.screen = self.return_screen;
-            } else {
-                self.return_screen = self.base_screen();
-                self.screen = Screen::Help;
-            }
+        if base_screen && is_key_pressed(KeyCode::F1) {
+            self.return_screen = self.base_screen();
+            self.screen = Screen::Help;
         }
         if is_key_pressed(KeyCode::F10) && self.screen != Screen::NameEntry {
             if self.screen == Screen::Settings {