Stack steering and follow-ups in colored boxes

[tmustier]

Summary

• restore bright lane-level colour with a blue steering box and yellow follow-up box
• label the delivery stages directly as next turn and after this run
• mute queued rows while keeping the live edited row bright
• keep message text at the same horizontal position before and during editing
• replace the demo with the stacked-box interaction

Verification

• npm run ci (30 tests)
• git diff --check
• npm pack --dry-run
• live Pi 0.80.9 proof while a tool streamed for 18 seconds
• visual review of full-terminal and queue-detail captures
• visual review of the updated 1× and 2× demo

The delivery model, queue ordering and keybindings are unchanged.