Same nested-dispose-in-onCleanup bug as 7f36ac2481 but in three more
places: TerminalProvider.disposeAll, PromptProvider.disposeAll, and
scoped-cache.clear() (covers viewCache.clear and comments cache.clear).
All of them synchronously call createRoot dispose() on cached entries
inside onCleanup, which during a server switch nests into the outer
cleanNode cascade and throws TypeError at chunk-*.js:992.
Snapshot the pending disposers, clear the cache synchronously, and
fire the disposers on a microtask so the outer cleanup finishes first.
LukeParkerDev