Replace all fmt.Errorf calls in runtime.go with structured errors via
coreerr.E() from go-log, ensuring every error carries operation context
for structured logging and tracing.
Add unit tests for runtime utilities (findFreePort, waitForHealth,
defaultProvidersDir), RuntimeManager (List, StopAll, StartAll),
ProvidersAPI (Name, BasePath, list endpoint), guiEnabled, and
staticAssetGroup. Coverage: 27.1%.
No os.ReadFile/os.WriteFile violations found. CLAUDE.md reviewed —
no outdated commands.
Co-Authored-By: Virgil <virgil@lethean.io>
