W64: Test for hex navigation Tab toggle

Add unit test verifying that Tab in hex mode toggles the
hexview_in_text flag (MC CK_ToggleNavigation parity).

Tests: 1423 pass (was 1422), zero warnings.

local/recipes/tui/tlc/source/src/viewer/mod.rs

@@ -1987,6 +1987,18 @@ mod tests {
         assert!(!v.show_help);
     }
 
+    #[test]
+    fn hex_navigation_tab_toggles() {
+        let p = make_hex_file("nav.bin", &[0x01, 0x02]);
+        let mut v = Viewer::open(&p).unwrap();
+        v.mode = ViewMode::Hex;
+        assert!(!v.hexview_in_text);
+        v.handle_key(Key::TAB);
+        assert!(v.hexview_in_text);
+        v.handle_key(Key::TAB);
+        assert!(!v.hexview_in_text);
+    }
+
     fn k(c: char) -> Key {
         Key { code: c as u32, mods: crate::key::Modifiers::empty() }
     }