refreshHostWakeBanner clears _hostWake before calling _hostWakeTick, so the
clear branch's `if (this._hostWake)` guard skipped the repaint: once the
banner had appeared for an unreachable remote session it stayed up on every
chat (local ones included) until a reload, and the 30s ticker never cleared
it either. Render unconditionally in that branch — _renderHostWakeBanner is
idempotent with a null state.
Reproduced in a real browser (Puppeteer, mobile viewport): state went null
but banner.hidden stayed false. Regression test added in
test/host-wake-banner.test.ts (red before, green after).
