fix(ir): reject non-type args to the 7 type-introspection builtins [F0.8]

size_of, align_of, field_count, type_name, type_eq, type_is_unsigned,
and is_flags silently reinterpreted a value argument as a type:
type_is_unsigned(6) read 6 as a TypeId index (types[6] = u8 -> true),
size_of(6)/size_of(true) sized its typeof (8), type_name(6) returned
types[6]'s name. Per Agra's ruling, all 7 now strictly require a type
(compile-time): a value argument is a compile error.

One shared guard (Lowering.reflectionTypeArgGuard, run at the top of
tryLowerReflectionCall) classifies each arg via reflectionArgIsType: a
spelled / compile-time type or generic type parameter (isStaticTypeArg),
or a runtime Type value (static type .any -- type_of(x), a []Type
element list[i], a Type-typed local/field/param) is accepted; anything
else is rejected with "<builtin> expects a type, got '<type>'". The
runtime path for type_name / type_is_unsigned is preserved (the {}
formatter calls type_is_unsigned(type_of(val)) at runtime). The 5
comptime-only builtins stay comptime-only (runtime reflection deferred).

Regression: examples/1144-diagnostics-reflection-builtin-needs-type.sx
(reject cases across all 7, exit 1). Unit test: reflectionArgIsType in
lower.test.zig. specs.md / readme.md document the strict type
requirement (and add the previously-undocumented align_of, type_eq,
type_is_unsigned). issues/0090 RESOLVED banner updated.

readme.md

@@ -432,7 +432,7 @@ The standard library (`modules/std.sx`) provides:
 - **Strings**: `concat`, `substr`, `int_to_string`, `uint_to_string`, `float_to_string`, `cstring`
 - **Memory**: `Allocator` protocol, `GPA` (general purpose), `Arena` (bump allocator)
 - **Math**: `sqrt`, `sin`, `cos`
-- **Introspection**: `type_of`, `type_name`, `type_is_unsigned`, `field_count`, `field_name`, `field_value`, `size_of`
+- **Introspection**: `type_of`, `type_name`, `type_is_unsigned`, `type_eq`, `field_count`, `field_name`, `field_value`, `size_of`, `align_of`, `is_flags` — the type-only builtins (`size_of`, `align_of`, `field_count`, `type_name`, `type_eq`, `type_is_unsigned`, `is_flags`) require a type argument (a spelled type, a generic `T`, or a runtime `Type` value); passing a value is a compile-time error
 
 ### Command-line interface (`modules/std/cli.sx`)