common: Add pre call bandwidth test

[thyal]

Description

Lets consumers measure a user's connection to the Whereby media servers before they join a room, so they can warn about a bad network up front.

core
PreCallTestClient, via client.getPreCallTest():

const preCallTest = client.getPreCallTest();

// runs for 15s by default; pass { durationSeconds } to change it (minimum 10)
const result = await preCallTest.startTest();

if (result?.warning) {
    console.log("Degraded connection", result.details);
}

// or drive your UI from state instead of awaiting
preCallTest.subscribeStatus((status) => {
    console.log("Pre-call test:", status); // idle | running | completed | failed
});

browser-sdk, the usePreCallTest hook:

import { usePreCallTest } from "@whereby.com/browser-sdk/react";

function MyNetworkCheck() {
    const { state, actions } = usePreCallTest();
    const { status, result, error } = state;

    return (
        <div>
            <button onClick={() => actions.startTest()} disabled={status === "running"}>
                {status === "running" ? "Testing…" : "Test my connection"}
            </button>

            {status === "completed" && result.success && <p>Your connection looks good.</p>}
            {status === "completed" && result.warning && (
                <p>Your connection may struggle: {result.details.recvAvailableBitrate.to
            )}
            {status === "failed" && <p>Could not test your connection: {error.message}</
        </div>
    );
}

success means no problems found. warning means the test completed but the connection is degraded — flags in details say which check tripped (lowRecvAvailableBitrate, highSendLoss, highRecvLoss). failed means no verdict at all, with error explaining why.

Network-only by design — no camera/mic/speaker steps, since those are user self-report rcover how to build those on top of useLocalMedia.

Summary:

Related Issue:

Testing

1. pnpm build && pnpm dev
2. Go to the Examples / Pre call test, bandwidth test story
3. Run the test
4. Verify that it works correctly (you can also check the network calls)
5. Throttle connection, and repeat the test
6. Verify that it shows degraded network

Screenshots/GIFs (if applicable)

Checklist

• My code follows the project's coding standards.
• Prefixed the PR title and commit messages with the service or package name
• I have written unit tests (if applicable).
• I have updated the documentation (if applicable).
• By submitting this pull request, I confirm that my contribution is made
  under the terms of the MIT license.

Additional Information

[changeset-bot]

🦋 Changeset detected

Latest commit: bac13d5

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 4 packages

Name	Type
@whereby.com/browser-sdk	Minor
@whereby.com/core	Minor
@whereby.com/assistant-sdk	Patch
@whereby.com/react-native-sdk	Patch

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