When --account N is passed, it should bypass env vars and load
accounts.csv row N directly. Previously, env vars were checked first
so the explicit --account flag had no effect when UNSANDBOX_PUBLIC_KEY
and UNSANDBOX_SECRET_KEY were set.
Correct credential priority (all 4 files):
1. Explicit -p/-k key flags
2. --account N → direct CSV row lookup (bypasses env vars)
3. UNSANDBOX_PUBLIC_KEY / UNSANDBOX_SECRET_KEY env vars
4. ~/.unsandbox/accounts.csv default (row 0)
5. ./accounts.csv default (row 0)
Files updated: un.sh (bash), un.lua, un.pl (perl), un.tcl
Also fixes load_accounts_csv in sh and tcl to support reading an
arbitrary row index rather than always returning the first line.
russell@unturf.com
ce327b35e9