The textual TUI (tui.py) is superseded by the web console (ratatoskr-web)
and is removed per the no-backwards-compat rule. The `ratatoskr` command
stays as a headless client: --send / --whoami / --characters /
--set-persona-pad / --seed-first-message still work; invoking it with no
--send now returns a usage error (rc 10) instead of launching the TUI.
Removed: src/ratatoskr/tui.py, tests/test_tui.py, the textual + textual-dev
deps, and cli.py's run_tui launch path. cli.py's shared exports (USER_AGENT,
ParsedArgs, formatters) stay — web/entrypoint.py and tier3.py depend on them.
BREAKING CHANGE: the interactive `ratatoskr --agent X` TUI is gone; use the
web console (ratatoskr-web) for interactive debugging, or --send for scripted.
Verified: full suite 520 passed; ratatoskr --help exit 0; no-send -> rc 10;
web/provider/tier3 import clean; textual absent from the lockfile.