feat(sketch): add markdown preview support

- Implement MarkdownPreviewHighlightSketch for markdown rendering
- Update SketchToolWindow to support markdown language
- Refactor updateViewText to improve markdown display

Author: phodal

core/src/main/kotlin/cc/unitmesh/devti/sketch/SketchToolWindow.kt

@@ -15,6 +15,7 @@ import cc.unitmesh.devti.observer.agent.AgentStateService
 import cc.unitmesh.devti.sketch.ui.ExtensionLangSketch
 import cc.unitmesh.devti.sketch.ui.LangSketch
 import cc.unitmesh.devti.sketch.ui.LanguageSketchProvider
+import cc.unitmesh.devti.sketch.ui.MarkdownPreviewHighlightSketch
 import cc.unitmesh.devti.sketch.ui.code.CodeHighlightSketch
 import cc.unitmesh.devti.util.AutoDevCoroutineScope
 import cc.unitmesh.devti.util.parser.CodeFence
@@ -285,6 +286,11 @@ open class SketchToolWindow(
                         langSketch?.onComplete(codeFence.text)
                     }
 
+                    val isCanHtml = codeFence.language.displayName.lowercase() == "markdown"
+                    if (isCanHtml && codeFence.isComplete && blockViews[index] !is ExtensionLangSketch) {
+                        langSketch = MarkdownPreviewHighlightSketch(project, codeFence.text)
+                    }
+
                     if (langSketch != null) {
                         val oldComponent = blockViews[index]
                         blockViews[index] = langSketch

core/src/main/kotlin/cc/unitmesh/devti/sketch/ui/MarkdownPreviewHighlightSketch.kt

@@ -45,9 +45,10 @@ class MarkdownPreviewHighlightSketch(val project: Project, val text: String) : E
 
     override fun updateViewText(text: String, complete: Boolean) {
         editorPane.text = convertMarkdownToHtml(text)
+        this.context = text
+
         editorPane.invalidate()
         editorPane.repaint()
-        this.context = text
     }
 
     override fun getComponent(): JComponent {