Introduce duSem to cap concurrent du subprocess spawns while keeping
the existing sem to limit overall scan fan-out (dir recursion/task concurrency).
This prevents du from monopolizing scan concurrency and reduces resource
spikes during folded-dir sizing.
Acquire semaphore before spawning goroutine in calculateDirSizeFast to prevent goroutine
explosion. Previously, all subdirectory goroutines were spawned immediately and blocked on
the semaphore—now the spawning itself is throttled.
- Implemented progress percentage display (e.g., `(45%)`) in `cmd/analyze` to show scanning status based on cached total files.
- Kept the UI clean by avoiding a full progress bar.
- fix: formatting improvements in `bin/touchid.sh`.
