fix(js-client-sdk): switching context does not update streaming connection (#1153)

**Requirements**

- [x] I have added test coverage for new or changed functionality
- [x] I have followed the repository's [pull request submission
guidelines](../blob/main/CONTRIBUTING.md#submitting-pull-requests)
- [x] I have validated my changes against all supported platform
versions

**Describe the solution you've provided**

Steaming connection will reset if the context key is different.

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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Changes streaming lifecycle behavior during `identify`, which can
impact connection churn and update delivery when applications frequently
switch contexts.
> 
> **Overview**
> Fixes context switching while streaming by **stopping the active
streaming data source on every `identify`** and then re-evaluating
streaming state, ensuring a new EventSource is created for the new
context.
> 
> Adds a regression test asserting that calling `identify` twice with
different contexts results in the stream being created twice (i.e.,
restarted).
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
fe84093. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: joker23

packages/sdk/browser/__tests__/BrowserDataManager.test.ts

@@ -460,6 +460,24 @@ describe('given a BrowserDataManager with mocked dependencies', () => {
     );
   });
 
+  it('restarts the stream when identify is called with a new context', async () => {
+    const context1 = Context.fromLDContext({ kind: 'user', key: 'user-1' });
+    const context2 = Context.fromLDContext({ kind: 'user', key: 'user-2' });
+    const identifyOptions: BrowserIdentifyOptions = {};
+    const identifyResolve = jest.fn();
+    const identifyReject = jest.fn();
+
+    flagManager.loadCached.mockResolvedValue(false);
+
+    dataManager.setAutomaticStreamingState(true);
+
+    await dataManager.identify(identifyResolve, identifyReject, context1, identifyOptions);
+    expect(platform.requests.createEventSource).toHaveBeenCalledTimes(1);
+
+    await dataManager.identify(identifyResolve, identifyReject, context2, identifyOptions);
+    expect(platform.requests.createEventSource).toHaveBeenCalledTimes(2);
+  });
+
   it('does not start a stream if identify has not been called', async () => {
     expect(platform.requests.createEventSource).not.toHaveBeenCalled();
     dataManager.setForcedStreaming(true);

packages/sdk/browser/src/BrowserDataManager.ts

@@ -102,6 +102,7 @@ export default class BrowserDataManager extends BaseDataManager {
 
       await this._finishIdentifyFromPoll(context, identifyResolve, identifyReject);
     }
+    this._stopDataSource();
     this._updateStreamingState();
   }