ir: bridgeType non-standard int widths intern the exact width, not s64

A signed/unsigned width other than 8/16/32/64 quantised to s64/u64, silently
changing the size. Intern the exact .signed/.unsigned width instead (the IR
supports arbitrary-width ints). The default tagged-union tag width
(tag_type orelse .s64) is kept -- it is a defined language default, not a
failed lookup. 236 + unit green.

src/ir/type_bridge.zig

@@ -79,14 +79,16 @@ pub fn bridgeType(ty: sx_types.Type, table: *TypeTable) TypeId {
             16 => .s16,
             32 => .s32,
             64 => .s64,
-            else => .s64,
+            // Non-standard width: intern the exact width rather than quantising
+            // to s64 (which would silently change the type's size).
+            else => table.intern(.{ .signed = w }),
         },
         .unsigned => |w| switch (w) {
             8 => .u8,
             16 => .u16,
             32 => .u32,
             64 => .u64,
-            else => .u64,
+            else => table.intern(.{ .unsigned = w }),
         },
         .f32 => .f32,
         .f64 => .f64,