fix: preserve lambda grouping and dialect JSON arrows

[minleejae]

A parenthesized single-parameter lambda such as arrayMap((x) -> x * 2, [1, 2]) loses its parameter parentheses when rendered, so reparsing changes its AST from LambdaExpression to JsonExpression. PostgreSQL and MySQL JSON access in later function arguments can also be incorrectly classified as a lambda.

Preserve explicit parameter grouping in LambdaExpression and share its rendering between toString() and the expression deparser, including the caller's body visitor. In PostgreSQL and MySQL/MariaDB presets, expression-list and parenthesized-operand arrow handling uses JSON access. Existing unparenthesized lambda rendering in the default parser remains available.

Validation: Gradle check passed (7498 tests, 0 failures, 0 errors, 25 skipped), including grammar ambiguity and static checks. New tests cover grouped single/multiple parameters, nesting, argument positions, custom deparsers, fast/complex parsing and missing JSON operands. Thirteen PostgreSQL/MySQL JSON fixtures and both rendered forms executed successfully on PostgreSQL 18.6 and MySQL 8.4.11 (39 executions).

Syntax references: PostgreSQL JSON operators, MySQL JSON extraction, ClickHouse lambda syntax.

[manticore-projects]

Thank you for fixing this, silent errors like those are the worst.