feat(asm): emit GOOBJ objects that link directly with the Go toolchain

Assisted-by: Qwen 3.8 Max Preview

parser/parser.go

@@ -375,6 +375,11 @@ func parseImmediate(g []token.Token) ast.Immediate {
 		if v, ok := tryInt(text); ok {
 			imm.Val = v
 			imm.HasVal = true
+		} else if u, err := strconv.ParseUint(text, 0, 64); err == nil && !imm.Neg {
+			// Unsigned 64-bit literals (DATA mask<>+8(SB)/8, $0x8000…)
+			// overflow int64; keep the bit pattern.
+			imm.Val = int64(u)
+			imm.HasVal = true
 		} else {
 			imm.Float = text
 		}