refactor: remove unused UserQuit error variant

The UserQuit error was initially added for ESC key handling but is not
used in the final implementation. All user exit scenarios are handled
through SessionState enum values instead.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: unhappychoice

src/cli/commands/game.rs

@@ -174,9 +174,5 @@ fn handle_game_error(e: GitTypeError) -> Result<()> {
             eprintln!("💡 This might be caused by unsupported language features");
             std::process::exit(1);
         }
-        GitTypeError::UserQuit => {
-            eprintln!("👋 Thanks for playing!");
-            std::process::exit(0);
-        }
     }
 }

src/error.rs

@@ -37,9 +37,6 @@ pub enum GitTypeError {
 
     #[error("Tree-sitter language error: {0}")]
     TreeSitterLanguageError(#[from] tree_sitter::LanguageError),
-
-    #[error("User quit")]
-    UserQuit,
 }
 
 impl GitTypeError {