Clean up logging in controller and wrap errors

[yushan8]

• Replaced common.WithReason with fmt.Errorf for error wrapping in getchangedtargets.go and getGraph.
• Promoted silent failures to hard errors — cache read failures, corrupt blobs, and cachedReader.Close() errors now return instead of logging and falling through.
• Surfaced ws.Release() errors in native_orchestrator.go via multierr.Append instead of swallowing them.
• Added logger.Error at each error return in top-level controller (GetTargetGraph, GetChangedTargets) with specific failure messages.
• Removed non-actionable logs — cache miss debug logs, bypass_cache logs, context cancelled logs.
• Removed unused logger param from compareTargetGraphs.
• Updated tests to match new error wrapping and removed ClassifiedError assertions where common.WithReason was replaced.