feat: add .gitignore for logs and refactor ServeSession to include path_roots in init_tree return

- Introduced a new .gitignore file to exclude log files from version control.
- Modified the `init_tree` function in `ServeSession` to return `path_roots`, enhancing the function's utility.
- Cleaned up commented-out code in `sourcemap.rs`, `patch_apply.rs`, and `tree.rs` for better readability and maintainability.

src/cli/sourcemap.rs

@@ -88,8 +88,6 @@ impl SourcemapCommand {
             filter_non_scripts
         };
 
-        // Pre-build a rayon threadpool with a low number of threads to avoid
-        // dynamic creation overhead on systems with a high number of cpus.
         rayon::ThreadPoolBuilder::new()
             .num_threads(num_cpus::get().min(6))
             .build_global()