Queue mid-turn follow-ups for non-steerable harnesses

[Warexpor]

Summary

• Queue busy mid-turn follow-ups whenever the active harness cannot steer, regardless of the selected follow-up behavior.
• Grok is the driver: its adapter advertises canSteer: false, so the default Steer setting no longer drops follow-ups or reports an error.
• Clarify the behavior in Settings and cover the queue decision with unit tests.

Test plan

• npm run check:web (119 test files, 1213 tests, and TypeScript check)
• Verified the branch starts from origin/main at 270b899