Fix binary operator reduction & associativity handling in parser; add operator precedence tests

[ChasLui]

Motivation

• Make binary operator reduction respect operator associativity (notably right-associative exponentiation) and improve multi-percent handling in the formula parser.

Description

• Replace the previous precedence-only list with BINARY_OPERATOR_GROUPS that pairs operator sets with an associativity flag and implement reduceBinaryOperators and applyInfixAt to correctly reduce operators by associativity.
• Make percent postfix parsing repeatable by changing the percent handling from OPTION to MANY so multiple % tokens are applied in sequence.
• Add @types/node to devDependencies and update the pnpm lockfile accordingly.
• Extend test/operators/testcase.ts with many operator-precedence and associativity cases (exponentiation chaining, unary minus vs exponent, chained comparisons, percent combinations, concatenation order, and others).

Testing

• Ran the unit test suite via npm run test, which includes the operator tests in test/operators/testcase.ts, and the tests passed.
• The updated operator test cases covering exponentiation associativity, multiple percent postfixes, chaining, and concatenation were executed and succeeded.

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Codex Task

[coveralls]

Coverage Report for CI Build 25848258237

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Coverage: 95.048%

Details

• Patch coverage: 31 of 31 lines across 1 file are fully covered (100%).

Uncovered Changes

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Coverage Stats

Relevant Lines:	5548
Covered Lines:	5284
Line Coverage:	95.24%
Relevant Branches:	2247
Covered Branches:	2125
Branch Coverage:	94.57%
Branches in Coverage %:	Yes
Coverage Strength:	10537.48 hits per line

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Keep exponentiation left-associative for Excel formulas

For Excel-compatible formulas, chained operators at the same precedence are evaluated left-to-right; Microsoft’s Excel precedence docs state this for same-precedence operators, so 2^3^2 should be reduced as (2^3)^2 (64), not 2^(3^2) (512). Marking ^ as right-associative changes results for any chained exponent formula and diverges from Excel behavior.

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