[codex] Migrate Docker resources to socket API

[RealDyllon]

Summary

Migrates Docker resource collection from per-refresh Docker CLI commands to Docker Engine API requests over the Colima Unix socket.

• Adds a lightweight Network.framework Unix-domain-socket HTTP client with timeout, status, content-length, and chunked-response handling.
• Adds SocketDockerResourceService to fetch containers, images, volumes, networks, stats, and disk usage from the Engine API while preserving the existing snapshot models.
• Updates backend aggregation to pass the Colima socket path instead of a Docker context string.
• Removes the Docker resource CLI implementation and the remaining docker context show diagnostics probe.
• Adds OpenSpec artifacts for the migration and replaces Docker resource tests with socket/API-focused coverage.

Validation

• openspec validate docker-socket-migration --strict
• xcodebuild test -project ColimaStack.xcodeproj -scheme ColimaStack -destination 'platform=macOS' -only-testing:ColimaStackTests
• xcodebuild test -project ColimaStack.xcodeproj -scheme ColimaStack -destination 'platform=macOS'