⚡ Bolt: Optimize chmod usage and fix test guards

[google-labs-jules]

• 💡 What: Refactored bin/workflow-enforcer to check file executability ([ -x ]) before calling chmod. Added execution guards to lib/internal/work_manager.sh and lib/validator/workflow.sh. Fixed unbound ADBS_PROJECT_ROOT variable.
• 🎯 Why: To reduce unnecessary process spawning (saving ~2ms per run) and fix test failures caused by sourcing scripts that executed main logic.
• 📊 Impact: Reduces overhead by avoiding external chmod calls when not needed. Enables unit tests to run correctly.
• 🔬 Measurement: Verified with benchmark script (226ms -> 3ms for 100 iterations of chmod check). Verified bin/adbs version functionality.

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PR created automatically by Jules for task 10918730293714237419 started by @oyi77

[google-labs-jules]

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