Fix proxy invariant crash when produce draft is returned from a getter (#2668)

setterTraps.get in store/modifiers now bypasses internal store symbols
($PROXY, $TRACK, $NODE, $HAS) and __proto__, mirroring the main store
proxy traps. Previously, reading $PROXY through the produce draft proxy
returned a freshly wrapped draft instead of the underlying store proxy,
violating the non-configurable data property invariant on the raw target.