refactor(devins-lang): use consistent language icon naming and extension handling

The commit refactors the DevInLanguage module to use a consistent naming convention for language icons and to handle file extensions more uniformly across the codebase.

Author: phodal

exts/devins-lang/src/main/kotlin/cc/unitmesh/devti/language/DevInIcons.kt

@@ -8,7 +8,6 @@ object DevInIcons {
     val DEFAULT: Icon = IconLoader.getIcon("/icons/devin.svg", DevInIcons::class.java)
     @JvmField
     val COMMAND: Icon = IconLoader.getIcon("/icons/devins-command.svg", DevInIcons::class.java)
-
     @JvmField
     val Terminal: Icon = IconLoader.getIcon("/icons/terminal.svg", DevInIcons::class.java)
 }

exts/devins-lang/src/main/kotlin/cc/unitmesh/devti/language/DevInLanguage.kt

@@ -4,7 +4,6 @@ import com.intellij.lang.Language
 
 object DevInLanguage : Language("DevIn", "text/devin", "text/x-devin", "application/x-devin") {
     val INSTANCE: Language = DevInLanguage
-
     override fun isCaseSensitive() = true
     override fun getDisplayName() = "DevIn"
 }

exts/devins-lang/src/main/kotlin/cc/unitmesh/devti/language/completion/provider/CodeFenceLanguageCompletion.kt

@@ -28,7 +28,7 @@ class CodeFenceLanguageCompletion : CompletionProvider<CompletionParameters>() {
     }
 
     private fun createLanguageIcon(language: Language): Icon {
-        return DeferredIconImpl(null, language, true) { curLanguage: Language -> curLanguage.associatedFileType?.icon }
+        return DeferredIconImpl(null, language, true) { it.associatedFileType?.icon }
     }
 
     private class MyInsertHandler : InsertHandler<LookupElement> {

exts/devins-lang/src/main/kotlin/cc/unitmesh/devti/language/psi/DevInFile.kt

@@ -23,7 +23,7 @@ class DevInFile(viewProvider: FileViewProvider) : PsiFileBase(viewProvider, DevI
          * Create a temp DevInFile from a string.
          */
         fun fromString(project: Project, text: String): DevInFile {
-            val filename = DevInLanguage.displayName + "-${UUID.randomUUID()}.devin"
+            val filename = DevInLanguage.displayName + "-${UUID.randomUUID()}." + DevInFileType.INSTANCE.defaultExtension
             val devInFile = PsiFileFactory.getInstance(project)
                 .createFileFromText(filename, DevInLanguage, text) as DevInFile