A pmg run as root with a preserved HOME (GitHub runners, sudo -E, su
without -) creates the invoking user's ~/.config/safedep as root-owned,
and event-log init then fail-closes every later non-root command.
Make that state self-solvable:
- event-log init permission errors exit with a usefulerror naming the
likely cause and the chown fix instead of a bare fatal
- pmg setup doctor probes event-log dir writability and reports the
same fix via a new per-result Fix override
- document the mechanism and remedy in system-install.md, along with
the binary ownership requirements for --system
- consolidate this branch's doctor tests into doctor_test.go
