feat: make CLI dependencies optional

[cindyrui71]

Summary

• add a default-enabled cli Cargo feature and require it for the cc-switch binary
• gate CLI/TUI modules and their direct dependencies so library consumers can build with default-features = false
• keep shared localization available to core library modules
• add CI coverage for the library-only build, test compilation, and all-target direct dependency boundary

Default builds remain unchanged: the cli feature is enabled by default.

Validation

• cargo check
• cargo test --lib --no-run
• cargo test --bin cc-switch --no-run
• cargo check --lib --no-default-features
• cargo check --lib --no-default-features --features test-hooks
• cargo test --lib --no-default-features --no-run
• cargo fmt --check
• git diff --check
• parsed .github/workflows/rust-ci.yml as YAML
• verified the all-target, no-default direct dependency graph excludes every feature-gated CLI/TUI dependency

Notes

cargo clippy still reports the existing reversed-empty-range lint in src/cli/tui/ui/home_chart.rs; this change does not touch that code.

[bytemain]

@SaladDay 你好，非常感谢开发这么棒的一个项目，我们在基于 cc-switch-cli 封装一个 napi-rs 的包装层，方便 Node.js 调用，napi-rs 这层就可以不依赖于 cli feature（可以减小包体积），希望官方可以考虑下 cli feature optional 的这个 PR。

[SaladDay]

@cindyrui71 @bytemain Thank you for the contribution and for explaining the napi-rs use case. This has now been merged.

The cli feature remains enabled by default for existing users, while library consumers can opt out with default-features = false. We also added Linux and Windows checks to protect this boundary.

Thanks again for helping improve cc-switch-cli!