The GBNF parser now correctly handles SORE's overloaded + operator:
- + inside (a+b+c) → alternation (not repetition)
- + outside parens → repetition
- +? and +* compound operators → normalized to Star
Also adds implicit concatenation when LPAREN follows a repetition,
so a+(b+c) parses as a+ followed by (b|c).
28 tests pass (13 new disjunction/compound tests). Full suite: 212 passed.