feat: show errors with --show-errors regardless of increase

[frankieyan]

Previously, --check-files and --stage-record-file with --show-errors would only display detailed errors when errors had increased. This made it inconsistent with check-all, which always shows errors when the flag is set.

Now --show-errors displays errors for all checked files that have errors, regardless of whether there's an increase:

🔍 Checking 1 file for React Compiler errors…
Errors:
    - src/bad-hook.ts: Line 6: Cannot access refs during render (x3)
✅ No new React Compiler errors in checked files

Test plan

Test locally by running against the sample project fixtures:

npm run build
cd src/__fixtures__/sample-project

• Create baseline records first

  node ../../../dist/index.mjs --overwrite

• --check-files --show-errors shows errors even with no increase

  node ../../../dist/index.mjs --check-files --show-errors src/bad-hook.ts

  🔍 Checking 1 file for React Compiler errors…
  Errors:
      - src/bad-hook.ts: Line 6: Cannot access refs during render (x3)
  ✅ No new React Compiler errors in checked files
  

• --stage-record-file --show-errors shows errors even with no increase

  node ../../../dist/index.mjs --stage-record-file --show-errors src/bad-hook.ts

  🔍 Checking 1 file for React Compiler errors and updating records…
  Errors:
      - src/bad-hook.ts: Line 6: Cannot access refs during render (x3)
  ✅ Records saved to .react-compiler.rec.json. No new React Compiler errors
  

• Errors still shown when there IS an increase (without baseline records)

  rm .react-compiler.rec.json
  node ../../../dist/index.mjs --check-files --show-errors src/bad-hook.ts

  🔍 Checking 1 file for React Compiler errors…
  Errors:
      - src/bad-hook.ts: Line 6: Cannot access refs during render (x3)
  ❌ React Compiler errors have increased in:
    • src/bad-hook.ts: +3
  
  Please fix the errors and run the command again.
  

[doistbot-app]

This change correctly updates the --show-errors flag to consistently display detailed error information for all checked files, regardless of whether there is an increase in errors. The implementation is sound and the accompanying integration tests thoroughly validate the new behavior, improving the tool's consistency and making its output more predictable for users.