An idle ACP session sets `deferAgentInitiatedTurns`, so a steered terminal
blocker routed through `sendCustomMessage({ triggerTurn: true })` was buried
in `#pendingNextTurnMessages` instead of starting a turn — invisible and
deferred to the next user prompt, the exact regression #5628 avoids.
`#routeAdvice` now preserves the blocker as a visible card when a turn cannot
auto-trigger (idle + ACP defer without an explicit allow), folding the
existing plan-mode preserve branch into the same guard.
Fixes#5628
roboomp
581bfed6b5