feat: add Intel macOS (x64) CI/CD support via GitHub Actions

[996superbot]

Summary

This PR adds GitHub Actions CI/CD to build and release wechat-cli binaries for all platforms, with a focus on enabling Intel macOS (x64) support which is currently missing.

Problem

• The npm package only ships a darwin-arm64 binary
• darwin-x64 platform directory exists but has no compiled binary
• No CI/CD pipeline exists to build platform-specific binaries
• Intel Mac users cannot use npm install -g @canghe_ai/wechat-cli

Changes

1. .github/workflows/release.yml (new)

Multi-platform GitHub Actions workflow with 6 jobs:

• macOS x64 — builds on macos-13 (Intel runner), compiles C key scanner for x86_64, PyInstaller packaging
• macOS arm64 — builds on macos-14 (Apple Silicon runner)
• Linux x64 / arm64 — builds on ubuntu-latest
• Windows x64 — builds on windows-latest
• Release — auto-creates a draft GitHub Release with all platform binaries attached

Triggered by v* tags or manual workflow_dispatch.

2. npm/wechat-cli/package.json (modified)

Added all platform packages to optionalDependencies:

• @canghe_ai/wechat-cli-darwin-x64
• @canghe_ai/wechat-cli-linux-x64
• @canghe_ai/wechat-cli-linux-arm64
• @canghe_ai/wechat-cli-win32-x64

This ensures npm install automatically fetches the correct binary for the user's platform.

Verification

The Intel macOS C binary (find_all_keys_macos.x86_64) has been compiled and tested locally on an Intel MacBook Pro (x86_64, macOS 14.8.3) — wechat-cli --help runs successfully.

Next Steps

After merging, the maintainer can:

1. Create a v0.2.5 (or next version) tag to trigger the workflow
2. Publish platform packages to npm (@canghe_ai/wechat-cli-darwin-x64, etc.)
3. The release will include pre-built binaries for all platforms