Fix model config compatibility and installer-owned uninstaller

[angnuoli]

Summary

• allow full-config saves to preserve unchanged future OpenClaw sections while rejecting unknown-section mutations
• make packaged and source-mode installs persist, verify, and roll back the PyInstaller uninstaller bundle before exposing Windows entry points
• add a side-effect-free packaged runtime check; keep bundle publication and uninstall registry failures fatal while treating shortcut failures as best effort
• compile the UTF-8 NSIS script explicitly so the single-file setup is produced reliably

Test plan

• python -m unittest discover -s tests -v (184 tests)
• npm --prefix desktop exec vitest run src/config-write-policy.test.ts (4 tests)
• cd desktop/renderer && npx vitest run src/components/ModelSetupDialog.test.ts (10 tests)
• powershell -ExecutionPolicy Bypass -File build.ps1
• dist\MicroClawInstaller\MicroClawInstaller.exe --check-uninstaller