⚡ Bolt: Prevent serialisation bottleneck by converting Scanner actors to structs

[acebytes]

💡 What: Converted CacheScanner and NodeModulesScanner from actor to struct and added explicit performance documentation.

🎯 Why: Using an actor to manage a withTaskGroup where child tasks invoke blocking methods on self inadvertently serializes the tasks on the actor's context, destroying parallelism. Since these scanners are stateless components that only interact with thread-safe dependencies (FileManager.default), actor isolation is unnecessary. Changing them to structs allows the recursive filesystem traversals and size calculations to run truly concurrently across multiple threads.

📊 Impact: Drastically reduces scan time for deep hierarchies and large file systems by unlocking true hardware parallelism.

🔬 Measurement: Verify by running the application and observing the time taken to complete a full scan of all cache categories and node_modules directories; the duration should be noticeably shorter, particularly on systems with many files.

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PR created automatically by Jules for task 6970769507282085271 started by @acebytes

[google-labs-jules]

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[acebytes]

Closing as superseded by merged #216 (NodeModulesScanner static/nonisolated refactor) + #206 (CacheScanner.scanCategory/directorySize marked nonisolated). The TaskGroup serialization bottleneck for both scanners is now resolved with the surgical nonisolated approach instead of converting actors to structs (CacheCleaner stays an actor since it isn't run in a TaskGroup).

[google-labs-jules]

Closing as superseded by merged #216 (NodeModulesScanner static/nonisolated refactor) + #206 (CacheScanner.scanCategory/directorySize marked nonisolated). The TaskGroup serialization bottleneck for both scanners is now resolved with the surgical nonisolated approach instead of converting actors to structs (CacheCleaner stays an actor since it isn't run in a TaskGroup).

Understood. Acknowledging that this work is superseded and stopping work on this task.