ZModel Schema Validation: Missing Datasource Should Be Rejected

[ymc9]

Current Problem:

• ✅ Multiple datasources are correctly rejected
• ❌ Missing datasource is incorrectly allowed (should fail)

Root Cause: The validation in /packages/language/src/validators/schema-validator.ts only checks for multiple datasources but doesn't validate the presence of
at least one datasource.

Proposed Solution:
if (dataSources.length === 0) {
accept('error', 'A datasource declaration is required', { node: model });
} else if (dataSources.length > 1) {
accept('error', 'Multiple datasource declarations are not allowed', { node: dataSources[1]! });
}