fix(parse): read a :: cast as a cast, not as a column name

[tiagolauer]

Fixes #277.

The bug

StrictRow<DB, 'select id::text as id_text from users'>  // QueryTypeError<'unknown column: id::text'>
StrictRow<DB, 'select id::text from users'>             // same

Loose mode is harmless ({ 'id::text': unknown }[]), but one cast column poisons the whole strict row. The :: syntax is clearly in-dialect for the library: $1::int in params is supported and tested.

The fix

':' is not in OperatorChar and nothing stripped a ::type suffix, so id::text fell through to BareColumnType as a literal column name.

A cast expression now resolves its operand and reports unknown for the column. That keeps the check where it is useful — a typo inside the cast still errors — without claiming a type the parser cannot know: the cast is what decides it, and SQL type names are not modelled here.

Verification

tests/cast-columns.test-d.ts, nine cases. Five red on master:

tests/cast-columns.test-d.ts(17,3): error TS2344: Type 'false' does not satisfy the constraint 'true'.
tests/cast-columns.test-d.ts(21,3): ...
tests/cast-columns.test-d.ts(25,3): ...
tests/cast-columns.test-d.ts(29,3): ...
tests/cast-columns.test-d.ts(37,3): ...

• aliased, bare, qualified, and beside ordinary columns — all clean in strict mode now
• naem::text still reports unknown column: naem, and p.id::text with no p source still reports unknown alias: p

Controls: loose mode is unchanged, a plain column is unchanged, and count(*)::int resolves through the same path.

tsc --noEmit clean, budget 194,259 (+1,773).