chore: rename app crate and binary to cyberpunk

The game is called cyberpunk; the city generator is its first subsystem,
not the project. The citygen library keeps its name. README reframed
around the game.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

crates/cyberpunk/Cargo.toml

@@ -1,11 +1,11 @@
 [package]
-name = "city"
+name = "cyberpunk"
 edition.workspace = true
 version.workspace = true
 license.workspace = true
 
 [[bin]]
-name = "city"
+name = "cyberpunk"
 path = "src/main.rs"
 
 [dependencies]

crates/cyberpunk/src/cli.rs

@@ -9,8 +9,8 @@ use std::path::PathBuf;
 
 #[derive(Parser)]
 #[command(
-    name = "city",
-    about = "Generate, explore and walk a cyberpunk city in the terminal"
+    name = "cyberpunk",
+    about = "A terminal roguelike in a multi-level cyberpunk city"
 )]
 pub struct Cli {
     #[command(subcommand)]

crates/cyberpunk/src/main.rs

@@ -1,4 +1,4 @@
-//! `city`: generate, explore and walk a cyberpunk city in the terminal.
+//! `cyberpunk`: a terminal roguelike in a multi-level cyberpunk city.
 
 mod anim;
 mod app;