fix: address Copilot review round 1 on #2318

- fetchTracking: count NDJSON streams line by line instead of leaving
  them at zero forever; justify the detached watcher promise; document
  that a partial SSE block at end-of-stream is dropped, as the SDK's own
  parser (no flush) and the SSE spec drop it.
- uncapturedBodyNote: case-insensitive content-type lookup, and a
  stream label (SSE / NDJSON) for the Network badge.
- InspectorClient: `openedAt` is when the response headers arrived, not
  when the GET went out; the snapshot copies its request records; a
  request the transport failed to send is rolled back out of the
  unanswered set via a new `trackSendFailure` callback; a raw-wire
  timeout is built as the SDK's own timeout shape and annotated the
  same way, so callers see one kind of timeout.
- Remote session storage revives the nested `stream.closedAt` Date.
- Hook test models a legacy double with `Object.defineProperty`, not a
  double cast.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01APKSYHGxXBUpnR7ErFiLJn
Signed-off-by: cliffhall <cliff@futurescale.com>

core/mcp/messageTrackingTransport.ts

@@ -24,6 +24,14 @@ export interface MessageTrackingCallbacks {
     message: JSONRPCNotification,
     origin: MessageOrigin,
   ) => void;
+  /**
+   * An outgoing request the base transport failed to send (the connection
+   * closed, the fetch failed before the frame reached the wire). Fires after
+   * `trackRequest` already recorded it, so a consumer keeping "requests still
+   * awaiting a response" can roll that entry back — a request that never went
+   * out is not unanswered (#2318).
+   */
+  trackSendFailure?: (message: JSONRPCRequest, error: unknown) => void;
 }
 
 /**
@@ -95,7 +103,12 @@ export class MessageTrackingTransport implements Transport {
           "client",
         );
       } else if ("method" in message) {
-        this.callbacks.trackRequest?.(message as JSONRPCRequest, "client");
+        const request = message as JSONRPCRequest;
+        this.callbacks.trackRequest?.(request, "client");
+        return this.baseTransport.send(message, options).catch((err) => {
+          this.callbacks.trackSendFailure?.(request, err);
+          throw err;
+        });
       }
     } else if ("method" in message) {
       this.callbacks.trackNotification?.(