Bring SCHEDULE_DESIGN_zh.md to the same reference-implementation
walkthrough shape as FEEDBACK_DESIGN_zh.md: it now assumes the spec has
been read, drops the mid-migration 'current state' warnings (the legacy
code is deleted), and covers what the old version predated -- the
commands chapter (UNSET three-state updates, ContextChange, why the
clock- and callback-driven writes stay plain methods), the adapters and
composition-root chapter (CAS field ownership, the corrupt-row error
split, the two anti-corruption layers and the inbound completion
listener), the dispatch journey with the three-driver macro diagram the
spec's §5.3 points at, and the test-layering table for the current
suites.
The spec's §6 marks the schedule slice done and drops the three
completed to-dos; the docs index gains the schedule walkthrough next to
its sibling.