⚡ Bolt: Replace actors with structs for truly parallel file scanning

.jules/bolt.md

@@ -0,0 +1,3 @@
+## 2024-03-30 - Replace actors with structs for parallel TaskGroups
+**Learning:** In Swift structured concurrency, using an `actor` to manage a `withTaskGroup` where tasks invoke synchronous, blocking I/O (like `FileManager` operations) directly on the actor inadvertently serializes the tasks, preventing parallelism.
+**Action:** For stateless components interacting with thread-safe dependencies (like `FileManager`), use `struct`s or `nonisolated` methods to allow tasks in a `TaskGroup` to execute concurrently across threads.

Sources/Cacheout/Scanner/CacheScanner.swift

@@ -1,13 +1,13 @@
 /// # CacheScanner — Parallel Cache Category Scanner
 ///
-/// An `actor` that scans all registered cache categories concurrently using
+/// A `struct` that scans all registered cache categories concurrently using
 /// Swift's structured concurrency (`TaskGroup`). Each category is scanned in
 /// its own child task for maximum parallelism.
 ///
 /// ## Thread Safety
 ///
-/// Uses the `actor` isolation model to ensure thread-safe access to internal state.
-/// All public methods are `async` and can be called from any concurrency context.
+/// Uses `struct` instead of `actor` to prevent inadvertently serializing
+/// synchronous `FileManager` operations inside the `TaskGroup`.
 ///
 /// ## Disk Size Calculation
 ///
@@ -26,7 +26,7 @@
 
 import Foundation
 
-actor CacheScanner {
+struct CacheScanner {
     private let fileManager = FileManager.default
 
     func scanAll(_ categories: [CacheCategory]) async -> [ScanResult] {

Sources/Cacheout/Scanner/NodeModulesScanner.swift

@@ -1,6 +1,6 @@
 /// # NodeModulesScanner — Recursive node_modules Finder
 ///
-/// An `actor` that recursively searches common developer project directories
+/// A `struct` that recursively searches common developer project directories
 /// for `node_modules` folders. Designed to find abandoned or stale dependencies
 /// that consume significant disk space.
 ///
@@ -28,7 +28,7 @@
 
 import Foundation
 
-actor NodeModulesScanner {
+struct NodeModulesScanner {
     private let fileManager = FileManager.default
 
     /// Common directories where developers keep projects