Fix unhandled rejections from "upstream ref ... is not a GitHub repo"

[Copilot]

When a workspace's branch upstream points at a non-GitHub remote (e.g., a parent folder with a non-GitHub origin), getPullRequestDefaults() throws BadUpstreamError. Two callers fail to handle this, producing repeated unhandled promise rejections in the Debug Console — matching the screenshot in the issue and likely correlating with the reported VS Code unresponsiveness, since the chat context provider re-fires on many events.

Changes

• src/lm/pullRequestContextProvider.ts — WorkspaceContextProvider.provideWorkspaceChatContext awaited getPullRequestDefaults() per folder with no try/catch. Wrap it, skip the offending folder, and debug-log its URI. This is the first stack in the screenshot:

  at getOrigin → getPullRequestDefaults → provideWorkspaceChatContext
  

• src/view/treeNodes/categoryNode.ts — The catch handler did e.response.status === 422, which throws TypeError for any error lacking .response (e.g. BadUpstreamError propagated from extractRepoFromQuery). Because the throw occurs inside the catch, it escapes as a second unhandled rejection (the getPullRequestsForQuery stack in the screenshot). Optional-chained the access:

  if (this.isCopilot && (e?.response?.status === 422) && e.message?.includes('the users do not exist')) {