Gate findings on the #108614 salvage (2c + simplify-code):
- CopilotACPProfile.fetch_models promised None on failure but raised (AuthError on a
missing CLI, RuntimeError/TimeoutError from the probe) — only the caller in
hermes_cli/models.py caught it; any other caller got exceptions. Wrap the body and
return None so the docstring and the base ProviderProfile.fetch_models contract hold.
- timeout_seconds was a PER-REQUEST budget (initialize + session/new each got the full
timeout => ~30s worst-case foreground stall on a hung CLI). One shared session deadline.
- /model --refresh (clear_provider_models_cache) wiped the disk cache but not the new
session memo, so a fresh CLI login stayed stale for 5 min past an explicit refresh.
- A failed probe is now memoized for 30s instead of the full 5 min, so signing in to
the CLI is picked up on the next switch.
- _fresh_acp_memo fixture restores the memo on teardown — no cross-test state leak.
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