Add CL/SQL-style symbol quoting using pipe delimiters for formula
identifiers. This allows category and item names that collide with
keywords (WHERE, SUM, IF, etc.) or contain special characters
(parens, operators, spaces) to be used unambiguously in formulas:
|WHERE| + |Revenue (USD)|
SUM(|Net Revenue| WHERE |Region Name| = |East Coast|)
Pipes produce Token::Ident (same as bare identifiers), so they work
everywhere: expressions, aggregates, WHERE clauses. Double-quoted
strings remain Token::Str for backward compatibility.
Also updates split_where and parse_where to skip/strip pipe delimiters.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
ab7e00a217