Serialize resolveCommentThread to fix race condition with rapid resolves

[Copilot]

Resolving multiple comment threads quickly in the PR webview causes resolved state to not persist. Each resolveCommentThread call runs a mutation then fetches the full timeline via _getTimeline(). When concurrent, the timeline re-fetch from an earlier call can return stale data (before a later mutation has propagated) and overwrite the webview state via updatePR({ events }).

• Added a _resolveCommentThreadQueue promise chain to PullRequestOverviewPanel that serializes resolve/unresolve operations, ensuring each mutation + timeline fetch completes before the next begins
• Optimistic UI updates in the webview React state still provide immediate visual feedback

private resolveCommentThread(message: IRequestMessage<...>) {
    this._resolveCommentThreadQueue = this._resolveCommentThreadQueue.then(async () => {
        // mutation + timeline fetch run sequentially per call
    });
}

[Copilot]

Pull request overview

This PR addresses a race condition in the Pull Request webview where rapidly resolving/unresolving multiple review threads could cause older timeline refreshes to overwrite newer resolved state.

Changes:

• Introduces a _resolveCommentThreadQueue promise chain to serialize resolve/unresolve operations.
• Updates resolveCommentThread to enqueue mutation + _getTimeline() refresh sequentially per request.

Show a summary per file

File	Description
src/github/pullRequestOverview.ts	Serializes review-thread resolve/unresolve operations to prevent stale timeline refreshes from overwriting newer state.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 2