HERMES_TUI_RESUME is an internal env var the Python wrapper exports to hand
a session ID off to the Ink TUI. Because _launch_tui started from
os.environ.copy(), any exported/stale value in the user's shell leaked
through — so plain `hermes --tui` would try to resume a missing session
and leave the UI at 'error: session not found' with no live session.
Drop HERMES_TUI_RESUME from the env before conditionally re-setting it
from the argparse-resolved resume_session_id. Tests cover both the drop
path and the set-from-arg path.
Salvage of #28080 by @noctilust.
noctilust
425aba766b