fix: remove bash from auto optimization workflow

[Pigbibi]

Summary

• stop asking Claude to use Bash in the auto optimization draft PR workflow
• add a timeout to the Claude step so failed automation exits faster
• cover the adjusted workflow contract in the workflow config test

Testing

• python3 -m unittest tests/test_prepare_auto_optimization_pr.py tests/test_auto_optimization_pr_workflow_config.py
• python3 -m py_compile scripts/prepare_auto_optimization_pr.py
• uvx ruff check scripts tests src
• ruby -e 'require "yaml"; Dir[".github/workflows/*.yml"].each { |f| YAML.load_file(f) }; puts "yaml ok"'