pct exec has a minimal PATH

`pct exec` runs with PATH=/sbin:/bin:/usr/sbin:/usr/bin — /usr/local/bin is excluded. Use full paths or `bash -lc` for tools installed there.

Many tools installed by helper scripts (e.g., `pihole`) land in `/usr/local/bin/`. Discovered during Pi-hole deployment (2026-02-26).
Affected entities:Pi-hole