feat: add validation for --human-readable flag usage with --list and --info modes only

Co-authored-by: aider (openai/andrew/openrouter/anthropic/claude-sonnet-4) <aider@aider.chat>

src/main.rs

@@ -271,6 +271,14 @@ fn main() -> Result<(), Error> {
         }
     }
 
+    // Validate human-readable usage
+    if args.options.human_readable && mode != KeepModes::List && mode != KeepModes::Info {
+        cmd.error(
+            ErrorKind::InvalidValue,
+            "--human-readable can only be used with --list and --info modes"
+        ).exit();
+    }
+
     debug!("MAIN: args: {:?}", args);
     debug!("MAIN: ids: {:?}", ids);
     debug!("MAIN: tags: {:?}", tags);