The script cd's into the fork dir for the clean-tree check (line ~202)
and never returns to PROJECT_ROOT. Every subsequent relative
'cd "$fork_dir"' subshell then fails with 'No such file or directory',
making single-fork and multi-fork runs always FAIL at the upstream-ref
resolution step. Make fork_dir absolute at assignment so all subshell
cd/git calls work regardless of current directory.
Found while attempting the base fork sync (verify-fork-functions gate).
vasilito
7e7ef73a8c