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");

e2e-tests/helpers/test_helper.ts

@@ -575,6 +575,13 @@ export class PageObject {
     await this.page.getByRole("button", { name: "Fix error with AI" }).click();
   }
 
+  async clickCopyErrorMessage() {
+    await this.page.getByRole("button", { name: /Copy/ }).click();
+  }
+
+  async getClipboardText(): Promise<string> {
+    return await this.page.evaluate(() => navigator.clipboard.readText());
+  }
   async clickFixAllErrors() {
     await this.page.getByRole("button", { name: /Fix All Errors/ }).click();
   }

e2e-tests/snapshots/fix_error.spec.ts_fix-all-errors-button-1.aria.yml

@@ -7,11 +7,12 @@
 - img
 - text: "src/pages/Index.tsx Summary: intentionally add first error"
 - img
-- text: Error
+- text: Error First error in Index...
+- img
+- button "Copy":
+  - img
 - button "Fix with AI":
   - img
-- text: First error in Index...
-- img
 - img
 - text: ErrorComponent.tsx
 - button "Edit":
@@ -19,11 +20,12 @@
 - img
 - text: "src/components/ErrorComponent.tsx Summary: intentionally add second error"
 - img
-- text: Error
+- text: Error Second error in ErrorComponent...
+- img
+- button "Copy":
+  - img
 - button "Fix with AI":
   - img
-- text: Second error in ErrorComponent...
-- img
 - img
 - text: helper.ts
 - button "Edit":
@@ -31,11 +33,12 @@
 - img
 - text: "src/utils/helper.ts Summary: intentionally add third error"
 - img
-- text: Error
+- text: Error Third error in helper...
+- img
+- button "Copy":
+  - img
 - button "Fix with AI":
   - img
-- text: Third error in helper...
-- img
 - button "Fix All Errors (3)":
   - img
 - button: