remote_update_cache=false unintentionally disables remote cache reads (remote_accept_cache has no effect)

Setting --remote_update_cache=false on rewrapper is supposed to prevent writing results to the remote cache while still accepting cache hits. In practice, it also disables remote cache reads, making --remote_accept_cache=true have no effect.

Steps to reproduce

rewrapper \
--remote_accept_cache=true \
--remote_update_cache=false \
--

Expected: cache hits are returned for previously cached actions.
Actual: every action executes as a cache miss, even when a valid cached result exists.

Start at the rewrapper handling for --remote_accept_cache and --remote_update_cache, then trace how those flags control remote cache reads and writes. Reproduce the issue with both flags enabled as shown and verify that existing remote cache hits are returned while new results are not written.

Written by the indexing model from the issue text.