Parse typed SQL literals and null modifiers

[nickapopolis]

Summary

• parse DATE and TIMESTAMP typed literals as atomic expressions
• preserve type keywords and trivia in the CST
• consume IGNORE NULLS / RESPECT NULLS correctly before window clauses
• expose the new TypedLiteral kind through the TypeScript package

Motivation

ClickHouse queries commonly use typed date and timestamp bounds, including inside BETWEEN expressions. Treating the type keyword and string as separate expressions causes cascading recovery diagnostics. The existing null-modifier parser also consumed whitespace rather than NULLS, which became visible when a modifier was followed by OVER.

Testing

• cargo test --quiet (544 tests passed)
• exercised typed literals in projections, function arguments, and BETWEEN bounds
• exercised mixed case and comments between the type and value
• exercised IGNORE NULLS OVER (...)

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