Preserve PR description when branch push fails during PR creation

[Copilot]

When the create-PR flow failed (e.g. an amended commit requires --force push), the user's typed title and description were silently replaced with the PR template the next time the webview re-rendered from persisted state.

Root cause

submit() in webviews/common/createContextNew.ts cleared the persisted webview state before awaiting pr.create:

const args = this.copyParams();
vscode.setState(defaultCreateParams); // wiped immediately
await this.postMessage({ command: 'pr.create', args });

On failure, the in-memory catch set createError, but the persisted state was already gone. Since the create view doesn't use retainContextWhenHidden, hiding/reopening the panel reloaded the webview from vscode.getState(), and handleMessage('pr.initialize') then fell back to defaultDescription because pendingDescription was undefined — restoring the template over the user's text.

Change

• Move vscode.setState(defaultCreateParams) to after the awaited pr.create round-trip in submit(). Reset only happens on success; on failure the user's title/description remain in persisted state alongside the new createError.

Cleanup on success paths is unchanged: _firstLoad reset and the 'reset' message dispatched from dispose() still clear state when the view is reopened.

// after
const args = this.copyParams();
await this.postMessage({ command: 'pr.create', args });
vscode.setState(defaultCreateParams); // only on success