feat(app): copy buttons for assistant messages and code blocks

packages/ui/src/components/message-part.tsx

@@ -673,14 +673,40 @@ PART_MAPPING["tool"] = function ToolPartDisplay(props) {
 
 PART_MAPPING["text"] = function TextPartDisplay(props) {
   const data = useData()
+  const i18n = useI18n()
   const part = props.part as TextPart
   const displayText = () => relativizeProjectPaths((part.text ?? "").trim(), data.directory)
   const throttledText = createThrottledValue(displayText)
+  const [copied, setCopied] = createSignal(false)
+
+  const handleCopy = async () => {
+    const content = displayText()
+    if (!content) return
+    await navigator.clipboard.writeText(content)
+    setCopied(true)
+    setTimeout(() => setCopied(false), 2000)
+  }
 
   return (
     <Show when={throttledText()}>
       <div data-component="text-part">
-        <Markdown text={throttledText()} cacheKey={part.id} />
+        <div data-slot="text-part-body">
+          <Markdown text={throttledText()} cacheKey={part.id} />
+          <div data-slot="text-part-copy-wrapper">
+            <Tooltip
+              value={copied() ? i18n.t("ui.message.copied") : i18n.t("ui.message.copy")}
+              placement="top"
+              gutter={8}
+            >
+              <IconButton
+                icon={copied() ? "check" : "copy"}
+                variant="secondary"
+                onClick={handleCopy}
+                aria-label={copied() ? i18n.t("ui.message.copied") : i18n.t("ui.message.copy")}
+              />
+            </Tooltip>
+          </div>
+        </div>
       </div>
     </Show>
   )