docs: README revamp — English-first with Chinese companion, spread-ready

Restructured after the token-watcher pattern: hook tagline and pitch
before badges, an honest-scope note, a why-ccmr comparison table (the
live-gateway vs config-switcher distinction is the product's core),
zero-friction npx setup CTA, and a real-transcript demo block instead
of a mockup.

README.md is now English (npm's landing page follows it); README.zh-CN
carries the full Chinese manual including the complete changelog, and
the two cross-link at the top. This changes the repo's README-language
convention per the owner's explicit direction. Operational content is
preserved: full zh command/model/config/scenario/troubleshooting docs;
EN keeps the compressed matrix and points to zh for the complete alias
table and history.

Author: luwill