- Remove core structural keywords from nonReserved so they cannot be
  used as identifiers: SELECT, FROM, WHERE, CREATE, TABLE, INSERT,
  UPDATE, DELETE, DROP, ALTER, SET, JOIN, GROUP, HAVING, ORDER, ON,
  UNION, INTERSECT, EXCEPT, INTO, NOT, AND, OR, IN, BETWEEN, LIKE,
  IS, EXISTS, CASE, WHEN, THEN, ELSE, END, CAST, AS, DISTINCT,
  PRIMARY, CONSTRAINT, REFERENCES, COLUMN, UNIQUE, CHECK, FOREIGN,
  RENAME, RECURSIVE, WITH, NULL, ESCAPE, NULLIF
- Add DIGIT_IDENTIFIER lexer token for identifiers starting with a
  digit (e.g. 123abc, 1st_column)
- Include DIGIT_IDENTIFIER in identifier rule alternatives

…tion

- Add GenericSqlListener and GenericSqlVisitor exports to src/index.ts
- Add GenericSQLOptions interface with configurable diagnostics flag
- Override validate() to return empty array when diagnostics disabled
- Export GenericSQLOptions type from src/index.ts

- Add exitQuerySpecification for QUERY_RESULT entity tracking
- Add exitSelectItem for column entity collection in SELECT clauses
- Track wildcard columns (ColumnDeclareType.ALL) for * and table.*
- Track expression columns with alias support (ColumnDeclareType.EXPRESSION)
- Stage previously untracked files (errorListener, splitListener, semanticContextCollector)