feat(core): add stream object api (#12841)

Close [AI-193](https://linear.app/affine-design/issue/AI-193)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **New Features**
- Added support for streaming structured AI chat responses as objects,
enabling richer and more interactive chat experiences.
- Chat messages now include a new field displaying structured stream
objects, such as reasoning steps, text deltas, tool calls, and tool
results.
- GraphQL APIs and queries updated to expose these structured streaming
objects in chat histories.
  - Introduced a new streaming chat endpoint for object-based responses.

- **Bug Fixes**
- Improved error handling for streaming responses to ensure more robust
and informative error reporting.

- **Refactor**
- Centralized and streamlined session preparation and streaming logic
for AI chat providers.
  - Unified streaming setup across multiple AI model providers.

- **Tests**
- Extended test coverage for streaming object responses to ensure
reliability and correctness.

- **Documentation**
- Updated type definitions and schemas to reflect new streaming object
capabilities in both backend and frontend code.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Co-authored-by: DarkSky <25152247+darkskygit@users.noreply.github.com>

packages/common/graphql/src/graphql/copilot-history-list.gql

@@ -14,6 +14,14 @@ query getCopilotHistories(
           id
           role
           content
+          streamObjects {
+            type
+            textDelta
+            toolCallId
+            toolName
+            args
+            result
+          }
           attachments
           createdAt
         }

packages/common/graphql/src/graphql/index.ts

@@ -617,6 +617,14 @@ export const getCopilotHistoriesQuery = {
           id
           role
           content
+          streamObjects {
+            type
+            textDelta
+            toolCallId
+            toolName
+            args
+            result
+          }
           attachments
           createdAt
         }

packages/common/graphql/src/schema.ts

@@ -137,6 +137,7 @@ export interface ChatMessage {
   id: Maybe<Scalars['ID']['output']>;
   params: Maybe<Scalars['JSON']['output']>;
   role: Scalars['String']['output'];
+  streamObjects: Maybe<Array<StreamObject>>;
 }
 
 export enum ContextCategories {
@@ -2195,6 +2196,16 @@ export interface SpaceShouldHaveOnlyOneOwnerDataType {
   spaceId: Scalars['String']['output'];
 }
 
+export interface StreamObject {
+  __typename?: 'StreamObject';
+  args: Maybe<Scalars['JSON']['output']>;
+  result: Maybe<Scalars['JSON']['output']>;
+  textDelta: Maybe<Scalars['String']['output']>;
+  toolCallId: Maybe<Scalars['String']['output']>;
+  toolName: Maybe<Scalars['String']['output']>;
+  type: Scalars['String']['output'];
+}
+
 export interface SubscriptionAlreadyExistsDataType {
   __typename?: 'SubscriptionAlreadyExistsDataType';
   plan: Scalars['String']['output'];
@@ -3374,6 +3385,15 @@ export type GetCopilotHistoriesQuery = {
           content: string;
           attachments: Array<string> | null;
           createdAt: string;
+          streamObjects: Array<{
+            __typename?: 'StreamObject';
+            type: string;
+            textDelta: string | null;
+            toolCallId: string | null;
+            toolName: string | null;
+            args: Record<string, string> | null;
+            result: Record<string, string> | null;
+          }> | null;
         }>;
       }>;
     };