feat(cql2-text): add modulo, integer division, and power arithmetic operators

[constantinius]

Implements three CQL2 arithmetic operators missing from the text parser:

• Modulo (%): e.g. 'attr % 2 = 0'
• Integer division (div): e.g. 'attr div 2 = 1'
• Power (^): e.g. 'attr ^ 2 = 4' (right-associative)

Changes span all layers:

• ast.py: adds ArithmeticOp.MOD/INTDIV/POW enums and Mod/IntDiv/Pow dataclasses
• cql2.py: extends ARITHMETIC_MAP with the three new operators
• grammar.lark: introduces a 'power' precedence level above 'product' for right-associative exponentiation; adds mod and intdiv production rules; uses named filter terminals (_PERCENT, _INTDIV) so they don't bleed into transformer callbacks
• parser.py: adds mod(), intdiv(), and pow() transformer methods
• tests: adds test_modulo, test_integer_division, test_power