fix: restore merged files and add PR test workflow

[YoungJinJung]

Summary

• fix merge damage in crypto_cmd.go, doctor_cmd.go, and crypto_cmd_test.go
• clean up the merged README quickstart flow for the new operator-safety features
• add a GitHub Actions test workflow so PRs automatically run go test ./cmd/ende ./internal/...

Validation

• go test ./cmd/ende ./internal/...
• checked for conflict markers outside vendor code

[amazon-q-developer]

This PR successfully resolves merge conflicts in three Go source files and adds a GitHub Actions test workflow. The changes restore proper code structure by removing duplicated import blocks in crypto_cmd.go, completing a truncated test function in crypto_cmd_test.go, and eliminating a duplicated loop in doctor_cmd.go. The README numbering fixes ensure the quickstart documentation flows correctly. All conflict markers have been properly resolved, and the code should now compile and run without issues. The addition of the automated test workflow will help catch issues in future PRs.

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