fix(exceptions): stop leaking internal type names in ParsingException

[pdevito3]

Summary

• ParsingException used to append the wrapped exception's raw Message text, which could include .NET type names and Sprache parser internals visible to an API client that shows the message.
• The message now shows only the line and column of a parse failure. The original exception stays on InnerException for full server-side detail.
• Message-text change only: same type, same base class, same constructor signature, no change to which inputs throw or which exception type they throw.

Test plan

• dotnet test QueryKit.UnitTests passes (386 tests)
• Added tests asserting the message has no System., Sprache., or type-name text for a bad operator, a bad logical operator, and a value the parser rejects
• Verified through the public API with the verify-querykit harness, against both an in-memory IEnumerable target and a real Postgres IQueryable target