feat(core): poll context docs and files embedding status (#10843)

Close [BS-2791](https://linear.app/affine-design/issue/BS-2791).

### What Changed?
- Add status filed to `CopilotContextDoc` to querying document embedding processing progress.
- Change `ChipState` from `success` to `finished` to better align with backend server status.
- Add `pollContextDocsAndFiles` API for embedding status polling.

### About Polling
- Set the minimum interval to 1 second and the maximum interval to 30 seconds
- Use exponential backoff and increase the interval by 50% after each poll
- Make sure the interval does not exceed the maximum

tests/affine-cloud-copilot/e2e/copilot.spec.ts

@@ -1026,7 +1026,7 @@ test.describe('chat with doc', () => {
     expect(await chipTitle.textContent()).toBe('Untitled');
     let chip = await page.getByTestId('chat-panel-chip');
     // oxlint-disable-next-line unicorn/prefer-dom-node-dataset
-    expect(await chip.getAttribute('data-state')).toBe('success');
+    expect(await chip.getAttribute('data-state')).toBe('finished');
 
     const editorTitle = await page.locator('doc-title .inline-editor').nth(0);
     await editorTitle.pressSequentially('AFFiNE AI', {
@@ -1048,7 +1048,7 @@ test.describe('chat with doc', () => {
 
     expect(await chipTitle.textContent()).toBe('AFFiNE AI');
     // oxlint-disable-next-line unicorn/prefer-dom-node-dataset
-    expect(await chip.getAttribute('data-state')).toBe('success');
+    expect(await chip.getAttribute('data-state')).toBe('finished');
 
     await typeChatSequentially(page, 'What is AFiAI?');
     await page.keyboard.press('Enter');
@@ -1071,6 +1071,6 @@ test.describe('chat with doc', () => {
     expect(await chipTitle.textContent()).toBe('AFFiNE AI');
     const chip2 = await page.getByTestId('chat-panel-chip');
     // oxlint-disable-next-line unicorn/prefer-dom-node-dataset
-    expect(await chip2.getAttribute('data-state')).toBe('success');
+    expect(await chip2.getAttribute('data-state')).toBe('finished');
   });
 });