The marketplace root was hardcoded to `~/.claude/plugins/marketplaces/thedotmack`,
which does not exist on XDG-compliant setups (e.g. Nix-managed Claude Code) where
plugins are stored under `~/.config/claude/plugins/`.
This caused an ENOENT error on every SessionStart:
ENOENT: no such file or directory, open
'~/.claude/plugins/marketplaces/thedotmack/package.json'
Now the script:
1. Derives the base path from CLAUDE_PLUGIN_ROOT if available
2. Probes the XDG path (~/.config/claude/plugins/...)
3. Falls back to the legacy path (~/.claude/plugins/...)
Fixesthedotmack/claude-mem#1030