Use Keycloak OAuth for a2amcp login

src/api.ts

@@ -1,7 +1,4 @@
-/**
- * Thin control-plane client. Mirrors the relevant subset of
- * a2a_pack.cli.api_client.ControlPlaneClient.
- */
+/** Thin control-plane client used with Keycloak bearer tokens. */
 export class ApiError extends Error {
   constructor(public status: number, message: string) {
     super(`API ${status}: ${message}`);
@@ -52,20 +49,6 @@ export class ControlPlaneClient {
     return (await resp.json()) as T;
   }
 
-  login(email: string, password: string) {
-    return this.request<{
-      access_token: string;
-      user: { id: number; email: string };
-    }>("POST", "/v1/auth/login", { email, password });
-  }
-
-  signup(email: string, password: string) {
-    return this.request<{
-      access_token: string;
-      user: { id: number; email: string };
-    }>("POST", "/v1/auth/signup", { email, password });
-  }
-
   me() {
     return this.request<{ id: number; email: string }>("GET", "/v1/me");
   }