Addresses audit findings from 2026-04-19:
- Q-H1: replace Println with Printf for %s-formatted error (line 42)
- Q-H2/Q-M2/Q-M3: verify_mount_dir and mount_sshfs now return error;
main exits on failure instead of continuing with invalid state
- Q-M1: default Port to "22" when ssh_config has no entry
- S-M1: create mount dir with 0700 instead of 0777
- S-M2: filepath.Clean + base-prefix check rejects HostName values
that would escape ~/Servers/
- Q-L1: correct "~/.ssh_config" typo to "~/.ssh/config"
Also: use os.Exit(2) for usage error (was 80), route user-facing
errors to stderr.
Replace minimal mount flags (dir_cache=no) with aggressive caching
and connection tuning: kernel_cache, attr/entry/negative timeouts,
fast cipher (aes128-gcm), reconnect with keepalive.
nevaforget