fix: delete expirer entry after proposal response

[ganchoradkov]

Description

Sign-client now correctly clears the expirer entry when it deletes a proposal. This was resulting in an annoying error log as the expirer couldn't find its target since the proposal was already deleted

Type of change

• Chore (non-breaking change that addresses non-functional tasks, maintenance, or code quality improvements)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Draft PR (breaking/non-breaking change which needs more work for having a proper functionality [Mark this PR as ready to review only when completely ready])
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How has this been tested?

tests, dogfooding

Checklist

• I have performed a self-review of my own code
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

Additional Information (Optional)

Please include any additional information that may be useful for the reviewer.

[Copilot]

Pull Request Overview

This PR fixes an issue where the expirer entry wasn’t cleared after a session proposal was deleted, preventing error logs due to missing targets.

• Added expirer.del(id) calls in both accept and reject flows in the engine controller
• Extended integration tests to assert expirer.keys state after proposal deletion
• Updated the release changeset to document the patch

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
packages/sign-client/src/controllers/engine.ts	Call this.client.core.expirer.del(id) immediately after deleting a proposal ID
packages/sign-client/test/sdk/client.spec.ts	Added assertions on clients.A.core.expirer.keys and their lengths in the integration test
.changeset/plain-paws-happen.md	Added patch notes for deleting expirer entries after proposal response

Comments suppressed due to low confidence (2)

packages/sign-client/test/sdk/client.spec.ts:96

• Consider adding an assertion to verify that the specific proposal ID is removed from expirer.keys (e.g., expect(clients.A.core.expirer.keys).not.to.include(id)) to ensure the entry was cleared.

expect(clients.A.core.expirer.keys).to.deep.equal(clients.B.core.expirer.keys);

packages/sign-client/test/sdk/client.spec.ts:100

• Consider adding a separate test case for the proposal rejection flow to ensure the expirer entry is also deleted in reject scenarios.

await deleteClients(clients);