Function getSchemaPrefix

getSchemaPrefix(schemaName: string): string
Returns the schema-based prefix for programmatic identifiers (class names, GraphQL types). This is the single source of truth for schema-to-prefix mapping, shared by both TypeScript codegen and SQL (via GetClassNameSchemaPrefix function in the database).

Special cases:
- __mj (core MJ schema) → "MJ"
- MJ (literal schema name) → "MJCustom" (prevents collision with core schema prefix)
- All others → sanitized schema name via sanitizeGraphQLName
Parameters
- schemaName: string
  The SQL schema name
Returns string
The clean prefix string to prepend to type/class names
Example
```
getSchemaPrefix('__mj')   // "MJ"
getSchemaPrefix('MJ')     // "MJCustom"
getSchemaPrefix('sales')  // "sales"
```
- Defined in packages/MJCore/src/generic/graphqlTypeNames.ts:112