Address @claude review: format core/, typed output-validation error, document progress heuristic

- Run Prettier on the 60 core/ files this PR touched — the deterministic
  import rewrite had collapsed multi-line imports and left throws unwrapped;
  core/ is in no format gate so it slipped past CI. Now Prettier-clean.
- Default-path output-schema violation now throws
  ProtocolError(ProtocolErrorCode.InvalidParams, …) instead of a bare Error,
  matching the prior v1 contract (SDK threw a typed McpError with a code) so
  downstream `instanceof`/`.code` branching keeps working.
- Document the "assumes serial construction" invariant on pollTaskToolCall's
  progress-subscription revival (the `_progressHandlers` new-key heuristic).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

core/auth/mcpAuth.ts

@@ -10,7 +10,14 @@
  * (the same path v2 `auth()` takes when refresh cannot widen scope).
  */
 
-import { auth as sdkAuth, discoverOAuthServerInfo, isHttpsUrl, registerClient, selectResourceURL, startAuthorization } from "@modelcontextprotocol/client";
+import {
+  auth as sdkAuth,
+  discoverOAuthServerInfo,
+  isHttpsUrl,
+  registerClient,
+  selectResourceURL,
+  startAuthorization,
+} from "@modelcontextprotocol/client";
 import type { OAuthClientProvider } from "@modelcontextprotocol/client";
 import type { FetchLike } from "@modelcontextprotocol/client";
 /**