docs: Add Rustdoc for modules, functions, and structs

Co-authored-by: aider (openai/andrew/openrouter/sonoma-sky-alpha) <aider@aider.chat>

src/main.rs

@@ -81,6 +81,7 @@ fn main() -> Result<(), Error> {
     tags.sort();
     tags.dedup();
 
+    /// Internal enum representing the parsed execution mode.
     #[derive(PartialEq, Debug)]
     enum KeepModes {
         Unknown,