test: cover deployment dump output

[Kkkakania]

Summary

• add deploy dump coverage for timestamped/latest files, network defaults, mainnet chain id, artifact metadata, source contents, and source read/hash mismatch errors
• restore process.exitCode after CLI failure-path tests so the full Jest run exits according to actual test results

Closes #1

Tests

• npm test -- --runInBand
• npx jest tests/deployDump.test.js --runInBand --coverage=false
• npm run check-format
• node --check tests/deployDump.test.js
• node --check tests/cli.test.js
• git diff --check