feat: add auth extension points and one ssh connect pipeline

src/backend/hosts/connect/core-providers.ts

@@ -0,0 +1,20 @@
+import { registerLegacySshAuthProviders } from "../../auth/legacy-providers.js";
+import { registerBuiltinSshAuthProviders } from "./builtin-providers.js";
+
+let registered = false;
+
+/**
+ * Registers core's providers once. Called lazily by the pipeline so tests and
+ * scripts get the same set as a running server without a start-up hook.
+ */
+export function ensureCoreSshAuthProviders(): void {
+  if (registered) return;
+  registered = true;
+  registerBuiltinSshAuthProviders();
+  registerLegacySshAuthProviders();
+}
+
+/** Test helper, pairs with resetSshAuthRegistryForTests. */
+export function resetCoreSshAuthProvidersForTests(): void {
+  registered = false;
+}