feat(error): create base Error enum

src/error.rs

@@ -0,0 +1,20 @@
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    // Domain errors
+    #[error("Invalid scope: {0}")]
+    InvalidScope(String),
+    #[error("Invalid description: {0}")]
+    InvalidDescription(String),
+    // Infrastructure errors
+    #[error("Not a Jujutsu repository")]
+    NotARepository,
+    #[error("jj is not installed or not in PATH")]
+    JjNotFound,
+    #[error("jj command failed: {message}")]
+    JjCommand { message: String, stderr: String },
+    // Application errors
+    #[error("Operation cancelled by user")]
+    Cancelled,
+    #[error("Non-interactive terminal detected")]
+    NonInteractive
+}

src/lib.rs

@@ -2,3 +2,4 @@ mod cli;
 mod commit;
 mod jj;
 mod prompts;
+mod error;