session.delete's body is rebound onto tui_gateway/server.py's globals by
bind_module, so the module-level import in methods_session.py was never
visible to it. Any exception in the try block then raised NameError while
evaluating the except clause: a live-turn delete crashed instead of
returning 4023, and a plain DB error that used to map to 5036 crashed too.
Import it in the handler body, the same way the module's other rebound
handlers pull in their dependencies.
Also update the test stubs whose delete_session signature predates the
exclude_active_write_guards kwarg, and the bulk-delete endpoint test that
now receives skipped_active: [].
d1849547e9