bug: invalid types for sessionIdGenerator in 1.25.2

[domdomegg]

SDK 1.25.2 introduced types that break projects using sessionIdGenerator: undefined with strict TypeScript configs.

Errors

error TS2379: Argument of type '{ sessionIdGenerator: undefined; enableJsonResponse: true; }'
is not assignable to parameter of type 'WebStandardStreamableHTTPServerTransportOptions' with
'exactOptionalPropertyTypes: true'.
  Types of property 'sessionIdGenerator' are incompatible.
    Type 'undefined' is not assignable to type '() => string'.

error TS2379: Argument of type 'StreamableHTTPServerTransport' is not assignable to parameter
of type 'Transport' with 'exactOptionalPropertyTypes: true'.
  Types of property 'onclose' are incompatible.
    Type '(() => void) | undefined' is not assignable to type '() => void'.
      Type 'undefined' is not assignable to type '() => void'.

Cause

Optional properties like sessionIdGenerator?: () => string need to be typed as sessionIdGenerator?: (() => string) | undefined to allow explicitly passing undefined.

Similarly, the Transport interface's onclose property needs the same treatment.

I beleive this was recently changed in #1326