The lexer now keeps token offsets and rejects what the grammar never allowed
but the token rules accepted:
- an empty phrase: "" (matched every card), tag:""
- a phrase touching a word or another phrase: a"b", "a"b, "a""b"
- whitespace between a qualifier and its phrase value: tag: "x"
key:"value" stays the only legal contact; parentheses still delimit phrases.
Listed in PLAN 6.1/6.2 and USAGE.