Add shebang and strict mode to perf script

[aobolensk]

• add a #!/usr/bin/env bash shebang
• enable set -euo pipefail for stricter error handling

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.15%. Comparing base (d1764d8) to head (7834f50).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #471   +/-   ##
=======================================
  Coverage   92.15%   92.15%           
=======================================
  Files          11       11           
  Lines         357      357           
  Branches      116      127   +11     
=======================================
  Hits          329      329           
  Misses         10       10           
  Partials       18       18           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.