Adding a button for copying error messages (#1882)

close #1870 





<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Adds a “Copy” button to error banners and chat error output so users can
quickly copy error messages with clear feedback. Addresses Linear #1870.

- **New Features**
- Introduced CopyErrorMessage component that writes to clipboard and
shows “Copied” for 2s.
- Added the copy button to the Preview error banner and DyadOutput;
actions grouped at the bottom beside “Fix with AI”.
- Added Playwright e2e test and helpers to verify copy behavior and
clipboard content.

<sup>Written for commit 12e9bf1437ded36dc022e1d795025580d2ffd111.
Summary will update automatically on new commits.</sup>

<!-- End of auto-generated description by cubic. -->

e2e-tests/fix_error.spec.ts

@@ -1,4 +1,5 @@
 import { testSkipIfWindows, test } from "./helpers/test_helper";
+import { expect } from "@playwright/test";
 
 testSkipIfWindows("fix error with AI", async ({ po }) => {
   await po.setUp({ autoApprove: true });
@@ -20,6 +21,26 @@ testSkipIfWindows("fix error with AI", async ({ po }) => {
   await po.snapshotPreview();
 });
 
+testSkipIfWindows("copy error message from banner", async ({ po }) => {
+  await po.setUp({ autoApprove: true });
+  await po.sendPrompt("tc=create-error");
+
+  await po.page.getByText("Error Line 6 error", { exact: true }).waitFor({
+    state: "visible",
+  });
+
+  await po.clickCopyErrorMessage();
+
+  const clipboardText = await po.getClipboardText();
+  expect(clipboardText).toContain("Error Line 6 error");
+  expect(clipboardText.length).toBeGreaterThan(0);
+
+  await expect(po.page.getByRole("button", { name: "Copied" })).toBeVisible();
+
+  await expect(po.page.getByRole("button", { name: "Copied" })).toBeHidden({
+    timeout: 3000,
+  });
+});
 test("fix all errors button", async ({ po }) => {
   await po.setUp({ autoApprove: true });
   await po.sendPrompt("tc=create-multiple-errors");