Add crypto agility review gates

[yanziwei]

Summary

Closes #1675.

• Adds Step 5.4 for cryptographic agility and migration evidence.
• Adds grep patterns for algorithm metadata, key IDs, migration paths, and legacy fallback code.
• Adds finding criteria for indefinite fallback, missing artifact versioning, fail-open algorithm handling, and unmeasured legacy data.
• Extends the output template with a cryptographic agility evidence table.
• Updates the skill version to 1.1.0.

Validation

• git diff --check
• Markdown fence balance check: 40 balanced
• Verified markers for version 1.1.0, Step 5.4, output evidence table, and the new common pitfall

Bounty request

Improver Moderate / $100 if accepted. Payment details can be provided privately after maintainer acceptance.