Holiday switch in the debug menu; darker wood for the treasury chests

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/holiday.rs

@@ -53,12 +53,27 @@ pub fn holiday_on(y: i64, m: i64, d: i64) -> u8 {
     }
 }
 
-// today's holiday (worked out once); on the desktop DUNGEONCRAFT_HOLIDAY=halloween / christmas /
-// easter / none shows one at any time
+thread_local! {
+    // the debug menu's choice: 0 by the date, else the holiday + 1
+    static OVERRIDE: std::cell::Cell<u8> = const { std::cell::Cell::new(0) };
+}
+
+// the debug menu's holiday setting (Settings::debug_holiday: 0 by the date, 1 none, 2 Halloween,
+// 3 Christmas, 4 Easter)
+pub fn set_override(v: u8) {
+    OVERRIDE.with(|o| o.set(v.min(4)));
+}
+
+// today's holiday (worked out once) unless the debug menu picks one; on the desktop
+// DUNGEONCRAFT_HOLIDAY=halloween / christmas / easter / none shows one at any time
 pub fn current() -> u8 {
     thread_local! {
         static HOLIDAY: std::cell::Cell<u8> = const { std::cell::Cell::new(255) };
     }
+    let forced = OVERRIDE.with(|o| o.get());
+    if forced > 0 {
+        return forced - 1;
+    }
     HOLIDAY.with(|h| {
         if h.get() == 255 {
             #[cfg(not(target_arch = "wasm32"))]