Ground the progressive chapter in why custom harnesses exist, the three
single-window failure modes, dynamic vs static, tasteful patterns, when
not to use workflows, and sharp neighbors (s06/s13/s15/s17).
Co-authored-by: Xinlu Lai <CrazyBoyM@users.noreply.github.com>
Retell the Runtime lesson as a progressive story (two doors, kitchen
primitives, null-isolation, longest-prefix resume) in EN/ZH/JA, and align
the mini-runtime with Claude Code / Pi semantics so the docs and code agree.
Co-authored-by: Xinlu Lai <CrazyBoyM@users.noreply.github.com>
