/tools' local handler silently returned for anything other than enable
or disable, so /tools list and friends looked broken even though the
Python CLI already implements them (hermes_cli/main.py registers
tools_sub for list/enable/disable).
Keep the client-owned enable/disable path (which has to run
session.setSessionStartedAt + resetVisibleHistory locally) and route
every other sub through slash.exec, matching createSlashHandler's
page/sys split for long vs short output.