feat: add native Windows plugin installation

[jasperyeoh]

Summary

• replace the Bash-only MCP launch path with a cross-platform Node launcher
• add Windows Python Launcher, UTF-8, LOCALAPPDATA, credential, and file-lock handling
• add native Windows/Ubuntu packaged-install CI and release smoke tests
• prepare version 0.2.2 documentation and changelog

Verification

• local Python: 100 passed, 1 Windows-only skipped
• local Node/frontend: 55 passed
• local TypeScript/package build passed
• packed fresh-venv MCP smoke passed in a Unicode/space path
• isolated DSH Web profile install, bundle patch, MCP discovery, and chart health passed
• GitHub Actions: Ubuntu/Python 3.10 and Windows Server 2025/Python 3.12 jobs passed, including packed ordinary-user install and isolated DSH Web profile startup

Remaining acceptance boundary

A physical Windows desktop DSH Web run is still required before the release notes should claim fully field-validated Windows support.