fix(test): stop the syncing-p tests leaking in-flight state

- They cleared the module's state hash on entry, not on exit.
- One marks "proton" syncing to exercise the dispatcher's in-flight guard.
- A sibling dispatch test uses a calendar also named "proton".
- ERT runs them in that order, so the dispatch became a no-op and it failed.
- Now each test let-binds a private hash, matching the sibling test files.
- Added a test that pins the isolation itself.

The failure was invisible from both directions. make test runs each file in its
own Emacs, and the editor hook skipped this family for exceeding its file cap.
It only appears when the 63 calendar-sync files run in one process.

0 files changed, 0 insertions, 0 deletions