teknium's review gap on #72021: the helper's worker/once-guard was
covered, but nothing asserted the stdio TUI entry point actually
invokes prewarm_picker_cache_async() — or that it does so in the right
place. Add a focused entrypoint test that runs the real entry.main()
with stubbed collaborators (same monkeypatch-module-attrs harness as
test_tui_entry_mcp_owner.py), spies on the helper in
hermes_cli.model_switch (the lazy-import source), and asserts:
- prewarm fires exactly once, strictly AFTER the gateway.ready write
- startup stays non-blocking: main() reaches the stdin loop and
returns on EOF
- a prewarm failure is swallowed (fire-and-forget) without breaking
startup
Mutation-checked: deleting the prewarm hunk from entry.py fails both
tests.
