feat(QueryBuilder): validate duplicate select columns

[elpete]

Summary

• add opt-in validation for duplicate select output names
• validate the final selection during SQL compilation so queries can be built and corrected out of order
• detect qualified columns, explicit aliases, subselect aliases, and explicitly aliased typed columns case-insensitively
• skip wildcards and expressions without explicit aliases whose output names cannot be determined safely
• document enabling the validation in development and leaving it disabled in production

Why

CFML query results silently collapse duplicate output labels, which can discard selected values when rows are converted to structs. This validation catches statically identifiable collisions before execution and recommends aliases.

Validation

• Added the failing tests first: 5 expected failures before implementation
• Focused select suite: 24 passed
• Full Lucee suite: 2,666 passed, 0 failed, 3 skipped
• CFFormat check
• git diff --check

Refs #105