Use global fetch instead of cross-fetch to eliminate node-fetch url.parse deprecation

[Copilot]

Users see [DEP0169] DeprecationWarning: url.parse() in the VS Code Window output. The warning originates from this extension: importing fetch from cross-fetch pulls in node-fetch@2.6.7 on the Node/desktop target, which calls the deprecated Url.parse() on every request.

The main REST path (@octokit/rest@22) already uses globalThis.fetch, so the remaining call sites were the only ones still routing through node-fetch: the Apollo/GraphQL link, avatar image fetches, the Copilot API, and enterprise-server detection.

Changes

• Drop cross-fetch imports in credentials.ts, githubServer.ts, common/uri.ts, and copilotApi.ts so these use the environment's global fetch (Node 20+ / browser), which is WHATWG-URL based and never calls url.parse().
• Add dom to lib in the Node tsconfig.json. DOM types (Element, BlobPart, DOM fetch/Response) were previously supplied transitively by cross-fetch's type defs (/// <reference lib="dom" />); this makes them explicit, matching the browser and test tsconfigs.

-import fetch from 'cross-fetch';
 import * as vscode from 'vscode';

Notes

• The node-fetch/url.parse() code is no longer present in the bundled output.
• cross-fetch remains as a dependency and its webworker webpack alias is left in place (now inert) to keep the change minimal and avoid lockfile churn; it can be removed in a follow-up.

[alexr00]

@copilot, will global fetch work in the browser?

[Copilot]

@copilot, will global fetch work in the browser?

Yes. In the browser/web-worker extension host, fetch is a native global (self.fetch), so it's available without any import. In fact cross-fetch's own browser build (browser-ponyfill.js) just re-exports that same global self.fetch, so switching to the global is behaviorally identical there — the only real change is on the Node target, where we drop node-fetch (and its deprecated url.parse()). The webworker bundle compiles and builds successfully.