Two new operator affordances powered by `HubAdmin.AskAi`:
* **Audit drill-down → "Explain" button.** Tappable on every
failed event when System AI is configured; greyed out with
a "Configure in Settings" tooltip otherwise. Shows an
inline panel under the event fields with the LLM's plain-
language explanation, a "FIX" suggestion, the privacy-mode
badge (`redacted` / `full`), and round-trip latency. Errors
map to actionable fix hints (`env_missing` → "set $VAR in
your shell, then fai daemon restart"; `network` → "is your
provider running?"; etc.) — no raw HTTP errors surfaced.
* **Settings dialog → System AI panel.** Renders the live
HubAdmin.SystemAiStatus (provider, endpoint, model,
api_key_env name, privacy mode). When disabled, shows a
one-line explainer + pointer to docs/architecture/system-ai.md.
Read-only for now; editing the config still requires
~/.fai/config.yaml (Phase-1+ adds in-place editing).
Both surfaces follow the new zero-learning-curve UX rule:
the user never has to look up what the configurable means or
how to fix an error — every state self-explains in place.
Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>