fix: use SHELL environment variable instead of user database for shell meta plugin

Co-authored-by: aider (openai/andrew.openrouter.qwen.qwen3-coder) <aider@aider.chat>

src/meta_plugin/system.rs

@@ -195,18 +195,7 @@ impl MetaPlugin for ShellMetaPlugin {
     fn finalize(&mut self) -> io::Result<String> {
         match env::var("SHELL") {
             Ok(shell) => Ok(shell),
-            Err(_) => {
-                // Try to get shell from passwd database using uid
-                match uzers::get_user_by_uid(get_current_uid()) {
-                    Some(user) => {
-                        match user.shell().to_str() {
-                            Some(shell) => Ok(shell.to_string()),
-                            None => Ok("unknown".to_string()),
-                        }
-                    },
-                    None => Ok("unknown".to_string()),
-                }
-            }
+            Err(_) => Ok("unknown".to_string()),
         }
     }