fix(test): test delete Windows registry accidently

[baka-gourd]

fix #4915

This PR is intended to fix the issue mentioned in the ticket regarding the accidental deletion of existing registry entries. However, while investigating the problem, we also discovered a concurrency issue in RegistryGuard, so the scope of the fix is quite extensive.

• Add per-test Windows registry isolation using a unique test UUID.
• Route Windows registry helpers through test-specific registry subkeys when a UUID is present.
• Update RegistryGuard to support multiple registry values and clean up the per-test registry subtree.
• Forward the registry UUID through the test Config and CliTestContext.
• Update Windows unit and integration tests to use UUID-scoped registry guards.
• Keep PATH registry checks and Programs entry checks isolated in tests.
• Treat missing registry keys or values as non-fatal during registry cleanup.
• No new UUID dependency is introduced; UUIDs are generated from rand.