Keep PostgreSQL case-insensitive pattern operators intact

[adenzhou1350]

Related to #613. Formatting 'a' !~* 'xyz' currently produces 'a' !~ * 'xyz': the lexer emits a comparison followed by a wildcard instead of one operator.

Recognize PostgreSQL's ~*, !~*, ~~* and !~~* as comparison tokens before the generic comparison rule. These are the case-insensitive regular-expression and LIKE operators documented in PostgreSQL's pattern-matching reference. Ordinary multiplication, SELECT wildcards, quoted operator text, and symbols separated by whitespace/comments retain their behavior.

<@ already works on the current base. This is independent of #920's @? repair and does not claim support for every PostgreSQL custom operator or every case in #613.

Validation on Windows / Python 3.14:

• Identical 17 focused regression/control cases: original source 13 failed, 4 passed; repaired source 17 passed.
• Full native suite: 523 passed, 2 xfailed, 1 xpassed; the original suite's xfail/xpass outcomes are unchanged.
• 64 operand/spacing/reindent cases preserve lexical tokens through formatting and are idempotent.
• Ruff and git diff --check pass.

AI-assisted implementation with independent native reproduction. No PostgreSQL server, cross-platform CI or performance claim.