Split Rust game src into modules; update AGENTS.md for dual toolchain

- Refactor apps/game/src/main.rs into modules: state.rs, camera.rs, ui/, gameplay/
- Add gameplay/galaxy_creation.rs scaffold (stubs only, no new logic)
- Update root AGENTS.md: separate TS workspace vs Rust game commands
- Update apps/AGENTS.md: docs/game/site use two toolchains, not one
- Add apps/game/AGENTS.md: build commands, module layout, naming conventions, Plugin pattern

apps/game/src/ui/main_menu.rs

@@ -0,0 +1,156 @@
+use bevy::prelude::*;
+
+use crate::state::AppState;
+
+// ── Markers ─────────────────────────────────────────────────────────────────
+
+#[derive(Component)]
+pub struct MainMenuUi;
+
+#[derive(Component)]
+pub enum MenuButton {
+    ContinueGame, //Needed for later once save game functionality is implemented, should have a check to see if a save game exists and only show this button if it does
+    NewGame,
+    Options,
+    Exit,
+}
+
+// ── Main Menu ───────────────────────────────────────────────────────────────
+
+pub fn setup_main_menu(mut commands: Commands) {
+    let button_style = Node {
+        width: Val::Px(280.0),
+        height: Val::Px(64.0),
+        justify_content: JustifyContent::Center,
+        align_items: AlignItems::Center,
+        ..default()
+    };
+
+    let button_text_font = TextFont {
+        font_size: 28.0,
+        ..default()
+    };
+
+    commands
+        .spawn((
+            Node {
+                width: Val::Percent(100.0),
+                height: Val::Percent(100.0),
+                display: Display::Flex,
+                flex_direction: FlexDirection::Column,
+                justify_content: JustifyContent::Center,
+                align_items: AlignItems::Center,
+                row_gap: Val::Px(24.0),
+                ..default()
+            },
+            BackgroundColor(Color::srgb(0.02, 0.02, 0.06)),
+            MainMenuUi,
+        ))
+        .with_children(|parent| {
+            // Title
+            parent.spawn((
+                Text::new("VOID::NAV"),
+                TextFont {
+                    font_size: 72.0,
+                    ..default()
+                },
+                TextColor(Color::srgb(0.7, 0.85, 1.0)),
+                Node {
+                    margin: UiRect::bottom(Val::Px(48.0)),
+                    ..default()
+                },
+            ));
+
+            // Subtitle
+            parent.spawn((
+                Text::new("A space exploration RPG"),
+                TextFont {
+                    font_size: 18.0,
+                    ..default()
+                },
+                TextColor(Color::srgb(0.4, 0.5, 0.6)),
+                Node {
+                    margin: UiRect::bottom(Val::Px(32.0)),
+                    ..default()
+                },
+            ));
+
+            // Start Game button
+            spawn_menu_button(
+                &mut parent.spawn_empty(),
+                "Start Game",
+                MenuButton::NewGame,
+                &button_style,
+                &button_text_font,
+            );
+
+            // Options button
+            spawn_menu_button(
+                &mut parent.spawn_empty(),
+                "Options",
+                MenuButton::Options,
+                &button_style,
+                &button_text_font,
+            );
+
+            // Exit button
+            spawn_menu_button(
+                &mut parent.spawn_empty(),
+                "Exit",
+                MenuButton::Exit,
+                &button_style,
+                &button_text_font,
+            );
+        });
+}
+
+fn spawn_menu_button(
+    cmd: &mut EntityCommands,
+    label: &str,
+    marker: MenuButton,
+    style: &Node,
+    text_font: &TextFont,
+) {
+    cmd.insert((
+        Button,
+        style.clone(),
+        BackgroundColor(Color::srgb(0.08, 0.1, 0.18)),
+        BorderColor(Color::srgb(0.3, 0.45, 0.7)),
+        BorderRadius::all(Val::Px(8.0)),
+        marker,
+    ))
+    .with_children(|btn| {
+        btn.spawn((
+            Text::new(label),
+            text_font.clone(),
+            TextColor(Color::srgb(0.75, 0.85, 1.0)),
+        ));
+    });
+}
+
+pub fn despawn_main_menu(mut commands: Commands, query: Query<Entity, With<MainMenuUi>>) {
+    for entity in &query {
+        commands.entity(entity).despawn();
+    }
+}
+
+// ── Button Interaction ──────────────────────────────────────────────────────
+
+pub fn main_menu_buttons(
+    mut next_state: ResMut<NextState<AppState>>,
+    mut exit: EventWriter<AppExit>,
+    interaction_query: Query<(&Interaction, &MenuButton), Changed<Interaction>>,
+) {
+    for (interaction, button) in &interaction_query {
+        if *interaction == Interaction::Pressed {
+            match button {
+                MenuButton::ContinueGame => next_state.set(AppState::InGame), // Placeholder for now
+                MenuButton::NewGame => next_state.set(AppState::GalaxyCreation),
+                MenuButton::Options => next_state.set(AppState::Options),
+                MenuButton::Exit => {
+                    exit.write(AppExit::Success);
+                }
+            }
+        }
+    }
+}