test(logo): deduplicate setup, drop internal-state assertions, nest describes

- Extract setupLogoEnv() helper to eliminate repeated 6-line beforeEach
  boilerplate (jest.clearAllMocks + globals + window/document patches)
  across all 22 describe blocks; parameterised with withFlute flag for
  the describe blocks that need instrument data populated.

- Remove assertions on private transport/scheduling fields that test
  implementation rather than observable behaviour: _transportEventId,
  _transportTime, delayParameters (runFromBlock Transport path and
  clearTurtleRun Transport path), delayTimeout (clearTurtleRun timeout
  path), _transportTime/_transportEventId (doStopTurtles Transport path),
  and _ignoringBlock (runLogoCommands already-running path). Tests now
  verify the externally observable outcome (correct callbacks fired,
  correct args passed) without coupling to internal cleanup state.

- Break large flat describe blocks into nested groups:
    Logo runFromBlock: step-mode / timeout / Transport scheduling
    Logo runFromBlockNow: flow block execution / limits and plugin
                          dispatch / profiling / completion callbacks
    Logo parseArg: value resolution / block type branches /
                   error and edge cases / plugin integration

Signed-off-by: Vanshika <pahalvanshikaa@gmail.com>

Author: vanshika2720