Run integration through the worker launcher

[rustyconover]

Summary

• place the main C# fixture worker behind the VGI launcher pool
• reuse one warm .NET process across repeated ATTACH operations
• keep the stateful writable and incompatible-protocol fixtures isolated
• enable the launcher-specific integration assertions

Validation

• bash -n and shellcheck on ci/run-integration.sh
• actionlint on both workflows
• git diff --check