- Move all linux_configuration scripts into two semantic categories:
- single_use/: scripts run once manually (fresh install, fixes, setup)
- periodic_background/: scripts run by systemd timers or daemons
- Preserve existing subdirectory structure within each category
- Fix lib/common.sh source paths for new directory depths
- Fix CONFIG_DIR depth in setup_periodic_system.sh and check_and_enable_services.sh
- Update all references in tests, fresh-install/main.sh, nix modules, and docs
- Fix check_polling_antipatterns.sh false positives (||, regex |, case patterns, jq strings)
- Fix pre-existing mypy exclusion path and type annotations for moved tools/ directory
- Rewrite check_polling_antipatterns.sh using awk (no bash regex loops); add require_serial: true
