Replace local detect-runner-os action with external detect-versions@v1 to
reduce custom action maintenance. Add architecture detection for future
cross-platform support and namespace all cache keys with "continuwuity-"
prefix to prevent collisions with other projects on shared runners.
Updates cache mount IDs in Dockerfiles to match the new namespacing
convention, ensuring consistent cache isolation across CI and Docker builds.
Separate fast release builds from slow max-perf builds to optimise runner
utilisation and provide quicker feedback. Release builds complete first with
standard optimisations, followed by Haswell-optimised dragrace builds once
the safe builds pass successfully.
Extract build logic into focused composite actions for better log visibility
in Forgejo UI. Split monolithic build action into prepare-docker-build,
inline docker build step, and upload-docker-artifacts to ensure each phase
completes independently and shows logs immediately.
Creates separate manifests at each stage to avoid waiting for all builds
before publishing.
