fix(computer-use): bundle native OCU runtime to remove desktop Node/PATH dependencies

[memory-lee]

The default open_computer_use configuration launches a system command, so desktop users cannot connect to the MCP server when OCU is not installed or Node is unavailable on PATH. This change pins open-computer-use@0.3.5 as a production dependency and resolves the default command to the bundled native executable's absolute path, while preserving user-specified commands.

• Unpack native files in both signed and unsigned macOS/Windows builds and exclude files for other platforms. macOS retains the complete OCU app bundle, which occupies approximately 3.8 MiB.
• Share command resolution between Settings dependency detection and MCP connections, log connection failures, and check for missing native executables during packaging.
• Add regression tests for platform paths, Settings detection, MCP connections, and actual ASAR packaging.
• Remove docs/github-yunxiao-sync.md.

Validation: all 54 MCP/Settings/path tests and 21 packaging tests passed in the isolated PR worktree. TypeScript, shell syntax checks, and git diff --check also passed. Local checks with a minimal PATH and an isolated ASAR fixture running under Electron's Node mode both completed real MCP handshakes and discovered nine tools.

Release validation still required: permissions, screenshots, clicks, and text input using the final signed installer on a clean machine, plus testing on Windows hardware. The tool discovery checks did not perform these desktop operations.