🧹 Refactor: Extract repeated separator to SEP variable in hooks

[sstklen]

🎯 What: Extracted the repeated hardcoded string ═══════════════════════════════════════════ to a SEP variable across three bash hooks (post-deploy-health.sh, post-edit-check.sh, pre-bash-guard.sh).
💡 Why: This reduces code duplication and improves maintainability by centralizing the separator variable, ensuring a single source of truth that is easier to update consistently.
✅ Verification: Verified changes by testing each script manually with typical arguments ("docker compose up", "app.js", "rm -rf /") and running shellcheck against all updated hook scripts. No errors were found.
✨ Result: Improved maintainability while preserving the identical command-line output behavior.

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PR created automatically by Jules for task 9731028728190547762 started by @sstklen

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