feat(devtools): enable auto lint and diff viewer by default

- Set enableAutoLintCode to true by default- Set enableDiffViewer to true by default
- Remove unnecessary comments and adjust layout in SingleFileDiffSketch

Author: phodal

core/src/main/kotlin/cc/unitmesh/devti/settings/coder/AutoDevCoderSettingService.kt

@@ -30,10 +30,10 @@ class AutoDevCoderSettingService(
         var trimCodeBeforeSend by property(false)
         var enableRenameSuggestion by property(false)
         var enableAutoRunTerminal by property(false)
-        var enableAutoLintCode by property(false)
+        var enableAutoLintCode by property(true)
         var enableRenderWebview by property(false)
         var enableAutoScrollInSketch by property(false)
-        var enableDiffViewer by property(false)
+        var enableDiffViewer by property(true)
         var teamPromptsDir by property("prompts") { it.isEmpty() }
 
         override fun copy(): AutoDevCoderSettings {