Bun.file: make exists()/size/lastModified reflect the current filesystem state - #33659

`view_size()` returns `0` for an *existing empty regular file* (`ISREG=true, st_size=0` → `max_size=0, seekable=Some(true)`), so `get_slice` hits the `this_size == 0` early exit and returns a store-less `init_empty` before any argument processing. This regresses the fresh-blob path (pre-PR the guard was `self.size.get() == 0` with `self.size == MAX_SIZE`, so the early exit was skipped): the slice loses its File backing — populate-then-`.text()` now reads `""` (the same read-poisoning class this 

`self.resolve_size()` here is the remaining sibling of the `self.size.set(...)` writes 7d808eaf removed from `get_size`: it caches a stat-derived size on the *original* blob, so `structuredClone(Bun.file(missing))` sets `self.size = 0` and a later `.text()` returns `""` — the exact #4930 shape with `structuredClone` in place of `exists()`. The call is not load-bearing (`store.serialize()` reads only `pathlike`, and the size-on-wire was already written at line 760), so it can simply be deleted to