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/mcp/inspectorClientEventTarget.ts

@@ -24,7 +24,17 @@ import type {
   ResourceReadInvocation,
   ResourceTemplateReadInvocation,
 } from "./types.js";
-import type { Tool, ServerCapabilities, Implementation, Root, Progress, ProgressToken, Task, CallToolResult, ProtocolError } from "@modelcontextprotocol/client";
+import type {
+  Tool,
+  ServerCapabilities,
+  Implementation,
+  Root,
+  Progress,
+  ProgressToken,
+  Task,
+  CallToolResult,
+  ProtocolError,
+} from "@modelcontextprotocol/client";
 import type { SamplingCreateMessage } from "./samplingCreateMessage.js";
 import type { ElicitationCreateMessage } from "./elicitationCreateMessage.js";
 import type { JsonValue } from "../json/jsonUtils.js";