Promote AgentCompany-New to the repository root and retire the old app

The legacy application - its src, tests, landing site, promo assets, docs,
release tooling, CI workflows, and root configs - leaves the tree; it stays
reachable in history. Everything under AgentCompany-New moves up unchanged:
same package name, so the production userData/database path is untouched,
and e2e/build scripts already resolved paths relative to the project. The
developer cred.txt stays gitignored at its new location. Full verify:ci
passes from the new root.

src/main/services/oauth/oauth-flows.ts

@@ -0,0 +1,23 @@
+import { githubCopilotFlow } from "./github-copilot-flow";
+import { openaiCodexFlow } from "./openai-codex-flow";
+import { antigravityFlow } from "./google-antigravity-flow";
+import { anthropicClaudeFlow } from "./anthropic-claude-flow";
+import type { OAuthFlow } from "./oauth-types";
+
+/** Provider keys (from the catalog) mapped to their native OAuth login flow. */
+const OAUTH_FLOWS: Record<string, OAuthFlow> = {
+  "github-copilot": githubCopilotFlow,
+  "gpt-account": openaiCodexFlow,
+  "google-antigravity": antigravityFlow,
+  "claude-pro": anthropicClaudeFlow,
+};
+
+export function hasOAuthFlow(providerKey: string): boolean {
+  return providerKey in OAUTH_FLOWS;
+}
+
+export function getOAuthFlow(providerKey: string): OAuthFlow {
+  const flow = OAUTH_FLOWS[providerKey];
+  if (!flow) throw new Error(`${providerKey} does not support interactive sign-in.`);
+  return flow;
+}