fix(sync-to-codex-plugin): exclude /.pi/ so the pi extension doesn't leak into the Codex plugin
The .pi/ directory holds the pi-harness extension (.pi/extensions/superpowers.ts),
which is tracked (not git-ignored), so the git-ignored-path exclusion helpers
never caught it. It was also missing from the static EXCLUDES list alongside the
other harness dotdirs (.opencode, .cursor-plugin, .claude-plugin), so a sync
would rsync pi's files into the Codex plugin distribution. Add /.pi/ to EXCLUDES.
Jesse Vincent