Force Cody panel repaint only for meaningful events (#8215)

Fixes
https://linear.app/sourcegraph/issue/QA-790/jb-specificmac-specific-chat-scroll-jumps-to-up-and-cody-ui-flickers

## Test plan

1. Launch any JetBrains IDE (e.g., IntelliJ IDEA, PyCharm) with the Cody
plugin installed.
2. Sign in to Cody using valid Enterprise account credentials.
3. In the Cody chat panel, prompt: "Write a Java/Python program" and
wait for the response.
4. Once the code is generated, scroll down to the bottom of the chat
output.
5. Hover your cursor over side panels icons next to Cody icon

**Expected behaviour:**

The Cody chat panel should maintain its current scroll position when
hovering over system UI elements.
There should be no flicker, movement, or unintended scroll jumps when
the cursor hovers over external system elements.

<!-- Required. See
https://docs-legacy.sourcegraph.com/dev/background-information/testing_principles.
-->

Author: pkukielka

jetbrains/src/main/kotlin/com/sourcegraph/cody/ui/web/WebviewView.kt

@@ -9,6 +9,7 @@ import com.sourcegraph.cody.agent.protocol_generated.Webview_ResolveWebviewViewP
 import java.awt.AWTEvent
 import java.awt.Toolkit
 import java.awt.event.AWTEventListener
+import java.awt.event.PaintEvent
 
 /// A view that can host a browser component.
 private interface WebviewHost {
@@ -30,7 +31,12 @@ internal class CodyToolWindowContentWebviewHost(private val owner: CodyToolWindo
   var proxy: WebUIProxy? = null
     private set
 
-  private var displayChangeListener = AWTEventListener { proxy?.forceRepaint() }
+  private var displayChangeListener = AWTEventListener { event ->
+    val updateRectSize = (event as? PaintEvent)?.updateRect?.size
+    if (updateRectSize == null || updateRectSize.height > 0 || updateRectSize.width > 0) {
+      proxy?.forceRepaint()
+    }
+  }
 
   override val viewDelegate =
       object : WebviewViewDelegate {