fix(desktop): the task note bar stays opaque when the task has finished

An ended task dimmed the whole note bar with opacity, so its paper turned
see-through and the transcript scrolling under the sticky bar read through it.
Only the bar's contents dim now, and the composer strip carries the
conversation dock's ramp to canvas so text fades out before it reaches the bar
and the finished line under it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: santoshkumarradha

desktop/src/features/conversation/tasks/task-composer.css

@@ -231,4 +231,12 @@ test('the task view follows the panel: an ended task says so and cannot take not
   await expect(page.getByText('This task has finished, so it cannot read a note.')).toBeVisible();
   await expect(page.getByRole('button', { name: 'Send note' })).toBeDisabled();
   await expect(page.locator('.task-view-body').getByText('Done', { exact: true })).toBeVisible();
+  // The transcript scrolls under the sticky bar: the ended bar keeps solid paper and its strip keeps the dock ramp.
+  const looks = await page.locator('.task-composer-bar').evaluate((bar) => {
+    const style = getComputedStyle(bar);
+    return { opacity: style.opacity, paper: style.backgroundColor, ramp: getComputedStyle(bar.parentElement!).backgroundImage };
+  });
+  expect(looks.opacity).toBe('1');
+  expect(looks.paper).not.toMatch(/rgba\(.*, 0(\.\d+)?\)$|transparent/);
+  expect(looks.ramp).toContain('linear-gradient');
 });