feat(eval): update eval.sop.md format and add usage guide link in README.md

[kangISU]

Summary

• Update eval.sop.md to match agent-sops-specification.md format
• Add Eval SOP usage guide link to README.md

Changes

eval.sop.md

• Add Parameters section with agent_path, evaluation_focus, test_case_count, and output_format
• Rename "Implementation Guidelines" to "Steps"
• Rename "Conversation Examples" to "Examples" with proper Example Input/Example Output format
• Remove all code examples of Strands Evals SDK because it's now available in Context7 for dynamical retrieval
• Preserve all detailed execution flows, bash commands, and file naming conventions

README.md

• Add usage guide link to the Eval SOP entry in the Available SOPs table
• Link: https://strandsagents.com/latest/documentation/docs/user-guide/evals-sdk/eval-sop/