v0.1.2

Split bilingual README, clarify /model switching and CC Switch role

Split the single bilingual README into English README.md (main entry)
and Chinese README-zh.md, with cross-links at the top of each file.

Clarify the usage example: once four model routes are configured in
Keyway, users can switch between them directly inside Claude Code via
the /model command — no restart or config change needed. CC Switch is
repositioned as an optional profile-management helper for organizing
default models across projects, not a requirement for switching.

Bump version to 0.1.2.

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