test(formatter): add corpus guards for pass interactions

[MayerTim]

Summary

• Add a Watcom corpus fixture for split ORDER BY IF ... THEN ... ELSE ... ENDIF continuations.
• Add a Watcom corpus fixture covering query clauses, CASE expressions, predicate function calls, inline IF expressions, procedural IF indentation, and block endings together.
• Preserve current formatter behavior with expected-output and idempotency checks.
• Keep this branch test-only with no extension behavior or default-setting changes.

Validation

• npm run test:corpus
• npm run validate
• npm run package:vsix

Notes

This PR is intentionally test-only. It strengthens formatter corpus coverage around high-risk pass interactions before any future formatter or tokenizer refactor work.