Rename galaxy_creation to galaxy; add character creation skeleton

- Rename GalaxyCreationPlugin -> GalaxyPlugin, AppState::GalaxyCreation
  -> AppState::Galaxy, module path galaxy_creation -> galaxy (folder
  rename preserves git history via git mv).
- Rename GalaxyCreationSpawned -> GalaxySpawned, despawn_galaxy_creation
  -> despawn_galaxy.
- Update AGENTS.md module layout, plugin pattern example, and naming
  table for the new names.
- Add apps/game/src/gameplay/character_creation/ skeleton: placeholder
  UI with Confirm (-> InGame) and Back (-> Galaxy) buttons plus Escape
  shortcut. Wired into main.rs via CharacterCreationPlugin.

apps/game/AGENTS.md

@@ -20,40 +20,44 @@ cargo test              # Run unit tests
 ```
 src/
 ├── main.rs              # App builder: plugins, state init, system registration
-├── state.rs             # AppState enum (MainMenu, GalaxyCreation, CharacterCreation, InGame, Options)
+├── state.rs             # AppState enum (MainMenu, Galaxy, CharacterCreation, InGame, Options)
 ├── camera.rs            # Camera spawn
 ├── ui/                  # UI screens (menus, HUD, etc.)
 │   ├── mod.rs
 │   └── main_menu.rs
 └── gameplay/            # Non-UI gameplay systems
     ├── mod.rs
-    └── galaxy_creation.rs
+    ├── character_creation/   # Character creation scene (skeleton)
+    ├── galaxy/              # Procedural galaxy inspection scene
+    ├── movement/            # Ship movement (kinematic + orbital)
+    ├── physics/             # Physics primitives (mass, gravity, etc.)
+    └── star_map/            # Star map data + visualization
 ```
 
 ### When to add a file vs a folder
 
-- **Default**: one file per feature (e.g. `main_menu.rs`, `galaxy_creation.rs`).
+- **Default**: one file per feature (e.g. `main_menu.rs`).
 - **Promote to a folder** when the file exceeds ~300 lines, mixes UI + logic + data, or needs shared private helpers.
 - A promoted folder should expose its public API via `mod.rs` and ideally bundle its systems into a Bevy `Plugin` (see pattern below).
 
 ### Plugin pattern (recommended once a folder exists)
 
 ```rust
-// src/gameplay/galaxy_creation/mod.rs
-pub struct GalaxyCreationPlugin;
+// src/gameplay/galaxy/mod.rs
+pub struct GalaxyPlugin;
 
-impl Plugin for GalaxyCreationPlugin {
+impl Plugin for GalaxyPlugin {
     fn build(&self, app: &mut App) {
-        app.add_systems(OnEnter(AppState::GalaxyCreation), setup_galaxy_creation)
-            .add_systems(OnExit(AppState::GalaxyCreation), despawn_galaxy_creation)
+        app.add_systems(OnEnter(AppState::Galaxy), setup_galaxy)
+            .add_systems(OnExit(AppState::Galaxy), despawn_galaxy)
             .add_systems(Update, (
                 /* update systems */
-            ).run_if(in_state(AppState::GalaxyCreation)));
+            ).run_if(in_state(AppState::Galaxy)));
     }
 }
 ```
 
-Then `main.rs` collapses to `app.add_plugins((..., GalaxyCreationPlugin))`.
+Then `main.rs` collapses to `app.add_plugins((..., GalaxyPlugin))`.
 
 ## Naming Conventions
 
@@ -61,13 +65,13 @@ Follows [Rust RFC 344](https://rust-lang.github.io/api-guidelines/naming.html).
 
 | Item | Convention | Example |
 |---|---|---|
-| Files, modules, directories | `snake_case` | `galaxy_creation.rs`, `main_menu.rs` |
+| Files, modules, directories | `snake_case` | `galaxy`, `main_menu` |
 | Crate name | `snake_case` | `void-nav` |
-| Structs, enums, enum variants | `UpperCamelCase` | `AppState`, `GalaxyCreation` |
+| Structs, enums, enum variants | `UpperCamelCase` | `AppState`, `Galaxy` |
 | Components | `UpperCamelCase` (suffix optional) | `Player`, `MainMenuUi` |
 | Resources | `UpperCamelCase` | `ClearColor`, `Time` |
 | States | `UpperCamelCase` + `State` suffix | `AppState`, `GameState` |
-| Plugins | `UpperCamelCase` + `Plugin` suffix | `GalaxyCreationPlugin` |
+| Plugins | `UpperCamelCase` + `Plugin` suffix | `GalaxyPlugin` |
 | Functions, systems, locals | `snake_case`, verb-first | `spawn_camera`, `setup_main_menu` |
 | Constants, statics | `SCREAMING_SNAKE_CASE` | `MAX_HEALTH` |