feat(lint): surface the amd64 extension layer's refusals

Assisted-by: GLM 5.3 Flash

asm/amd64_ext.go

@@ -71,6 +71,26 @@ func amd64ExtStatement(mnem string, ops []*ast.Operand) (extops []arch.ExtOperan
 	return out, true, nil
 }
 
+// EncodeAmd64Statement runs one parsed amd64 statement through the layer
+// exactly as the assembler does: the operands convert the amd64ExtOperand way
+// and the mnemonic resolves and encodes through the registry.  pinned reports
+// that the statement belongs to the layer alone (the mnemonic is registered
+// and the scalar paths cannot encode it); err is the layer's own refusal of
+// the operands, the same text the assembler prints, so the linter surfaces
+// one diagnostic where assembly would fail.  A statement the scalar paths own
+// returns pinned false, with nothing to report.
+func EncodeAmd64Statement(mnem string, ops []*ast.Operand) (code []byte, pinned bool, err error) {
+	extops, pinned, err := amd64ExtStatement(mnem, ops)
+	if !pinned || err != nil {
+		return nil, pinned, err
+	}
+	code, err = EncodeExtension(arch.AMD64, mnem, extops...)
+	if err != nil {
+		return nil, true, err
+	}
+	return code, true, nil
+}
+
 // amd64ExtOperand converts one parsed operand into the layer's form: a $ immediate,
 // a vector, general or opmask register, or a base-relative memory operand, each
 // with the brace decorations the spelling carries.