test: add output formatter and printer tests

[sonukapoor]

Summary

• add unit tests for output recommendation, serialization, sorting, and cache/info/warn formatting in src/output/formatters.ts
• add unit tests for summary, action summary, table, final status, and compact output rendering in src/output/printers.ts
• capture console output with deterministic assertions so user-facing text regressions are easier to catch

Testing

• npm test
• npm run build

Closes #59