Title screen, pause menu, settings dialog and savegames

- title screen (continue/new/load/settings/help) and Esc pause menu
- settings: language & sound, camera, graphics, game, rebindable keys;
  stored in localStorage and in every savegame (always applied on load)
- savegames as JSON (.dcsave): download, load via file picker or drag & drop
- autosave to localStorage every 2 minutes and when the tab is hidden/closed
- configurable wall detail, light count, interface size, game speed, hints
- audio behind a cargo feature so native tests run (cargo test --no-default-features)
- savegame round-trip test

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

src/game.rs

@@ -1,6 +1,7 @@
 // Game logic: units, AI, economy, hero waves.
 
 use crate::map::*;
+use serde::{Deserialize, Serialize};
 
 pub const CORE_HP: f32 = 2000.0;
 pub const GATE_HP: f32 = 3000.0;
@@ -71,7 +72,7 @@ pub struct SfxEvent {
 pub const MANA_MAX: f32 = 400.0;
 pub const CARRY_MAX: i32 = 300;
 
-#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Serialize, Deserialize)]
 pub enum EK {
     Worker,
     Kobold,
@@ -112,7 +113,7 @@ pub fn st(k: EK) -> St {
     }
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Serialize, Deserialize)]
 pub enum Job {
     None,
     Dig(usize),
@@ -129,7 +130,7 @@ pub enum Job {
     Rally,
 }
 
-#[derive(Clone)]
+#[derive(Clone, Serialize, Deserialize)]
 pub struct Ent {
     pub id: u32,
     pub kind: EK,
@@ -217,6 +218,7 @@ pub struct Fx {
     pub col: u32,
 }
 
+#[derive(Serialize, Deserialize)]
 pub struct Game {
     pub map: Map,
     pub ents: Vec<Ent>,
@@ -231,7 +233,9 @@ pub struct Game {
     pub warned: bool,
     pub portal_timer: f32,
     pub payday: f32,
+    #[serde(skip)]
     pub fx: Vec<Fx>,
+    #[serde(skip)]
     pub msgs: Vec<Msg>,
     pub state: u8, // 0 running, 1 victory, 2 defeat
     pub paused: bool,
@@ -241,14 +245,17 @@ pub struct Game {
     pub gate_hit_t: f32,
     pub gate_stage: u32, // defender thresholds triggered (0..3)
     pub flag: Option<usize>,
+    #[serde(skip)]
     pub events: Vec<SfxEvent>,
     pub last_wave_value: f32,
     pub torches: Vec<Torch>,
+    #[serde(skip)]
+    pub hints: bool, // show hint messages (setting)
     hint_t: [f32; 16],
 }
 
 // torch on a wall face: wall tile + direction (index into DIR4) towards the open side
-#[derive(Clone, Copy, PartialEq)]
+#[derive(Clone, Copy, PartialEq, Serialize, Deserialize)]
 pub struct Torch {
     pub wall: usize,
     pub dir: usize,
@@ -315,6 +322,7 @@ impl Game {
             events: Vec::new(),
             last_wave_value: 0.0,
             torches: Vec::new(),
+            hints: true,
             hint_t: [-1000.0; 16],
         };
         let (cx, cy) = g.map.core;
@@ -391,7 +399,7 @@ impl Game {
     }
 
     fn hint(&mut self, slot: usize, key: &'static str) {
-        if self.time - self.hint_t[slot] > 30.0 {
+        if self.hints && self.time - self.hint_t[slot] > 30.0 {
             self.hint_t[slot] = self.time;
             self.msg(key, vec![]);
         }