Sinon.restore() also restores sandboxes in 21.1.0

[ar7bd]

Describe the bug
After update to 21.1.0 the global Sinon.restore() also restores individual sandboxes.

To Reproduce
Steps to reproduce the behavior:

const sandbox = Sinon.createSandbox();

const foor = { bar: () => 'baz' };
sandbox.stub(foor, 'bar').returns('qux');
assert.strictEqual(foor.bar(), 'qux'); // as expected

Sinon.restore(); // Used to not touch sandbox before

assert.strictEqual(foor.bar(), 'qux'); // This fails after 21.1.0

Expected behavior
I couldn't find this explicitly in the documentation. But my expectation is the old behavior, that creating a dedicated sandbox means my stubs are handled only by that. I used that a lot to have stubs in test tools which are not cleared by any local Sinon.restore() in tests.

Screenshots
N/A

Context (please complete the following information):

• Sinon version : 21.1.0
• Runtime: Node 24.14.1 and 25.8.0
• Output of npx envinfo --browsers --binaries:

  Binaries:
    Node: 25.8.0 - /usr/local/bin/node
    Yarn: 1.22.22 - /usr/local/bin/yarn
    npm: 11.11.0 - /usr/local/bin/npm

• Additional information: It looks like this is triggered by createSandbox nesting any new sandboxes to the global sandbox in src/create-sinon-api.js:

createSandbox: function createSandbox(config) {
    const s = createConfiguredSandbox(config);
    sandbox.getFakes().push(s);
    return s;
},

In 21.0.0 I don't see this nesting behavior: https://github.com/sinonjs/sinon/blob/v21.0.0/lib/sinon/create-sandbox.js

I did not investigate further. Please confirm whether the current behavior should be retained or if my expectation is incorrect.