ci: add dry-aged-deps for dependency freshness checks

[tompahoward]

Summary

• Install dry-aged-deps as a dev dependency for supply-chain-safe dependency freshness monitoring
• Add .dry-aged-deps.json config with exclusions (with reasons) for all 20 currently outdated packages
• Add dry-aged-deps --check as a post-build step in the GitHub Actions build workflow
• Add dry-aged-deps --check to the pre-push husky hook
• Add .yarnrc with --ignore-engines for Node 20+ compatibility with eslint-plugin-jsdoc

Test plan

• dry-aged-deps --check exits 0 with all current outdated deps excluded
• All existing tests pass (5/5, 100% coverage)
• Pre-push hook runs successfully with the new check
• Spellcheck passes with the new config file excluded
• Projen regeneration preserves all changes

https://claude.ai/code/session_01HNvBcQzT1SviRqkUpP5Xce

[mergify]

❌ The current Mergify configuration is invalid

Details

• Extra inputs are not permitted @ root → pull_request_rules → item 0 → actions → queue → method → squash
• Extra inputs are not permitted @ root → pull_request_rules → item 0 → actions → queue → commit_message_template → {{ title }} (#{{ number }})

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[mergify]

❌ The current Mergify configuration is invalid

Details

• Extra inputs are not permitted @ root → pull_request_rules → item 0 → actions → queue → method → squash
• Extra inputs are not permitted @ root → pull_request_rules → item 0 → actions → queue → commit_message_template → {{ title }} (#{{ number }})

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[mergify]

❌ The current Mergify configuration is invalid

Details

• Extra inputs are not permitted @ root → pull_request_rules → item 0 → actions → queue → method → squash
• Extra inputs are not permitted @ root → pull_request_rules → item 0 → actions → queue → commit_message_template → {{ title }} (#{{ number }})

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[mergify]

❌ The current Mergify configuration is invalid

Details

• Extra inputs are not permitted @ root → pull_request_rules → item 0 → actions → queue → method → squash
• Extra inputs are not permitted @ root → pull_request_rules → item 0 → actions → queue → commit_message_template → {{ title }} (#{{ number }})

{{ body }}

[mergify]

❌ The current Mergify configuration is invalid

Details

• Extra inputs are not permitted @ root → pull_request_rules → item 0 → actions → queue → method → squash
• Extra inputs are not permitted @ root → pull_request_rules → item 0 → actions → queue → commit_message_template → {{ title }} (#{{ number }})

{{ body }}