Fix column param metadata generation

[rmorehig]

Summary

• skip required and description keyword emission for p.column() parameters
• keep positional default injection so p.column().optional("lastSeen") generates {{ column(orderBy, 'lastSeen') }}
• add regression coverage for Tinybird's column() template helper behavior

Docs checked

• Tinybird query parameter docs document column() separately as {{column(order_by, 'timestamp')}} and recommend the second positional default argument.
• The generic description=... / required=... signature is shown for typed dynamic parameters, while column() examples do not use those kwargs.

Verification

• pnpm vitest run src/generator/pipe.test.ts src/schema/params.test.ts
• pnpm typecheck