refactor(completion): adjust caret movement and input size

- Modify caret movement logic in `CustomAgentCompletion` to insert a space and move caret by one character.
- Set preferred height of input field in `AutoDevInputSection` to

Author: phodal

core/src/main/kotlin/cc/unitmesh/devti/gui/chat/AutoDevInputSection.kt

@@ -155,6 +155,7 @@ class AutoDevInputSection(private val project: Project, val disposable: Disposab
             }
             customRag.selectedItem = defaultRag
 
+            input.preferredSize = Dimension(input.preferredSize.width, 48)
             layoutPanel.addToLeft(customRag)
         }
 

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

@@ -8,6 +8,7 @@ import com.intellij.codeInsight.completion.CompletionProvider
 import com.intellij.codeInsight.completion.CompletionResultSet
 import com.intellij.codeInsight.lookup.LookupElementBuilder
 import com.intellij.util.ProcessingContext
+import kotlinx.html.dom.document
 
 class CustomAgentCompletion : CompletionProvider<CompletionParameters>() {
     override fun addCompletions(
@@ -17,11 +18,11 @@ class CustomAgentCompletion : CompletionProvider<CompletionParameters>() {
     ) {
         val configs: List<CustomAgentConfig> = CustomAgentConfig.loadFromProject(parameters.originalFile.project)
         configs.forEach { config ->
-            result.addElement(LookupElementBuilder.create(config.name)
+            result.addElement(
+                LookupElementBuilder.create(config.name)
                 .withInsertHandler { context, _ ->
-                    context.editor.caretModel.moveCaretRelatively(
-                        1 + config.name.length, 0, false, false, false
-                    )
+                    context.document.insertString(context.tailOffset, " ")
+                    context.editor.caretModel.moveCaretRelatively(1, 0, false, true, false)
 
                     val toolWindow = AutoDevToolWindowFactory.getToolWindow(context.project)
                     toolWindow?.contentManager?.contents?.map { it.component }?.forEach {