fix: bound auto optimization prompts

[Pigbibi]

Summary

• export only the selected low-risk task summary into the Claude prompt
• add claude_args: --max-turns 8 so auto optimization runs do not wander too long

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"'