CLI-to-local-daemon RPC: relative file paths resolve against the daemon's cwd, not the CLI's

Common pattern in course distributed-systems projects: a thin CLI sends a command over RPC (e.g. Go net/rpc) to a long-running daemon on the same host, passing a local filename for the daemon to read or write (put key file / get key file). If the CLI forwards a relative path, the daemon opens it relative to its own working directory (often set by tmux -c or a launcher script), so the file silently goes somewhere else or isn't found. Fix: have the CLI make the path absolute (filepath.Abs) before sending, or have the CLI do the file I/O itself and send/receive bytes. Related pitfall from the same review: reusing the gossip RPC timeout (~500ms) for KV calls breaks large (1 MiB + fsync) writes, so give data-path RPCs their own size-scaled timeout.