feat: restore spies automatically with using

[privatenumber]

Problem

spyOn() replaces an object's property until the test calls .restore(). If a test returns early or throws first, the replacement can remain installed and affect later assertions.

ECMAScript explicit resource management defines [Symbol.dispose]() as the synchronous cleanup hook for using declarations. TypeScript's using documentation specifies that this cleanup also runs when a scope exits through an error or early return.

For example, using request = spyOn(service, 'request') had no cleanup behavior, so test authors needed a try/finally block to guarantee restoration.

Closes #57

Changes

spyOn() results now expose [Symbol.dispose]() as the existing .restore() operation. Tests can scope a replacement to a block and have the original property restored automatically:

{
  using request = spyOn(service, 'request').willCall(mockRequest)

  // `service.request` is mocked here.
}
// `service.request` is restored here.

The runtime hook is defined only when Symbol.dispose exists, so the package continues to load on its supported older Node.js versions. The new behavior covers normal scope exit and error unwinding.

[privatenumber]

@sheremet-va Addressed!

[sheremet-va]

LGMT!