chore: remove xmake, clean up unused files, simplify CLI parsing (#392)

## Summary
- **Remove xmake build system**: delete `xmake.lua`, `test-xmake.yml`
workflow, and all xmake-related pixi tasks
- **Migrate packaging to CMake**: `publish-clice.yml` now uses `cmake
-DCLICE_RELEASE=ON` instead of xmake pack
- **Clean up**: remove unused `tests/uv.lock`, `.xmake/` from
`.gitignore`, xmake references from docs
- **Benchmark CI**: change trigger from `pull_request` to
`workflow_dispatch` (manual only)
- **Simplify CLI parsing**: use `DecoKV(style =
KVStyle::JoinedOrSeparate)` in `clice.cc` and `unit_tests.cc`, replacing
verbose `DecoKVStyled` with manual `static_cast` bitmask; use comma
separators; explicit `names` only for underscore fields

## Test plan
- [x] `pixi run cmake-build RelWithDebInfo` compiles successfully
- [x] Verify `pixi run test` passes
- [x] Verify `pixi run package` produces correct archives via CMake
release build
- [x] Verify benchmark workflow can be triggered manually via `gh
workflow run benchmark`

🤖 Generated with [Claude Code](https://claude.com/claude-code)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Chores**
* Consolidated CI workflows; some automated triggers converted to manual
invocation
* Standardized shell for workflow steps and removed legacy build
workflow
* Switched packaging/build tasks to a CMake/Ninja flow and updated
artifact paths
  * Adjusted ignore rules to include previously-ignored build metadata

* **Documentation**
* Removed XMake-specific build and test instructions; docs now reflect
the CMake-based workflow

* **Style**
* Updated CLI option declaration style (no user-facing flag name
changes)

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/zh/dev/test-and-debug.md

@@ -18,13 +18,6 @@ $ ./build/bin/unit_tests --test-dir="./tests/data"
 $ pytest -s --log-cli-level=INFO tests/integration --executable=./build/bin/clice
 ```
 
-如果你使用 xmake 作为构建系统，可以直接通过 xmake 运行测试：
-
-```shell
-$ xmake run --verbose unit_tests
-$ xmake test --verbose integration_tests/default
-```
-
 ## Debug
 
 如果想在 clice 上附加调试器并进行调试，推荐先单独以 socket 模式启动 clice，然后再将客户端连接到 clice 上