⚡ Bolt: [performance improvement] batch branch deletion in script.ps1

[Cylae]

💡 What: Refactored the local branch cleanup logic in script.ps1 to batch all target branch names into a single array and pass them to one git branch -D command instead of calling it repeatedly inside a loop.

🎯 Why: In PowerShell, spawning native executables (like git) carries significant overhead. The original code exhibited an N+1 performance bottleneck by spawning a new git process for every single branch to be deleted.

📊 Impact: Reduces the number of process spawns during cleanup from O(N) to O(1), drastically speeding up the cleanup phase, especially in repositories with many stale branches.

🔬 Measurement: Execute the script in a repository with multiple branches to delete. Measure total execution time before and after the change; the cleanup phase will complete almost instantaneously with the patch.

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PR created automatically by Jules for task 298510120052178563 started by @Cylae

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