Keep playerbots from re-engaging during danger retreat

[adrunkhuman]

• Bot One recognized excessive damage and began returning to depot, but immediately engaged an adjacent Valkyrie that did not block its route. It stayed in place, exhausted its potions, and died.
• Keep danger retreat active across navigation and service resets. Reject optional combat, preserve healing priority, and defer level-eight departure until retreat ends.
• Try detours first. Allow each confirmed route blocker one five-second combat attempt without chase or immediate reacquisition. Restore ordinary defense at depot arrival or the next hunt.
• Add pure retreat-policy checks and a captured-log assertion for optional engagement, blocker reacquisition, and incomplete or fatal returns.

Escape is not guaranteed when trapped. The exact danger-transition encounter still needs post-fix live observation; there is no dedicated deterministic live fixture yet.