Pure code moves, no behaviour change. The session-interrupt gateway
handlers (methods_session_interrupt.py) and the CLI session-tool
handlers (cli_commands_session_tools.py) leave the two ratchet-offset
monoliths they lived in, so the module-size ratchet offsets can be
reclaimed. cli_commands_mixin re-imports the moved names so existing
'from cli_commands_mixin import _t' consumers keep working.
