fix(0112): out-of-range int literals error instead of silently wrapping

checkIntLiteralFits range-checks a literal against its integer target
(builtins + custom widths via intLiteralRange; width-64 types skip —
every representable literal is a legal bit pattern there) and diagnoses
with the type's range and an xx/cast hint. Wired into the .int_literal
arm (covers decls, assignments, call args, struct-literal fields),
lowerStructConstant, and globalInitValue.

A negated literal now folds to a single constant so -128 range-checks
as -128 rather than as an out-of-range +128 intermediate. An explicit
xx operand skips the check — truncation stays available on request
(cast(T) was already exempt: its value arg lowers without the target).

examples/0300-closures-lambda.sx pinned 133 wrapping to -3 through an
s3 param — the exact class this outlaws; updated to a fitting value.

Found during the fix and filed separately: issue 0113 (negated-literal
global initializers rejected as non-constant; pre-existing).

Regressions: examples/1156-diagnostics-int-literal-out-of-range.sx,
examples/0174-types-int-literal-boundaries.sx.

src/ir/lower/decl.zig

@@ -976,7 +976,10 @@ pub fn globalInitValue(self: *Lowering, vd: *const ast.VarDecl, var_ty: TypeId)
     return switch (v.data) {
         .undef_literal => .zeroinit,
         .null_literal => .null_val,
-        .int_literal => |il| .{ .int = il.value },
+        .int_literal => |il| blk: {
+            self.checkIntLiteralFits(il.value, var_ty, v.span);
+            break :blk .{ .int = il.value };
+        },
         .bool_literal => |bl| .{ .boolean = bl.value },
         // A float initializer at an integer-typed global follows the
         // implicit narrowing rule (integral folds, non-integral errors).