Extract mutation from Validate method into separate defaulting logic

Summary

The validateEmbeddingServer method on VirtualMCPServer mutates r.Spec.Config.Optimizer during validation — a defaulting operation hidden inside a validation function. The mutation is never persisted to the API server, is re-applied every reconciliation from a fresh cache copy, and is invisible to users via kubectl get.

Severity: MUST FIX
Area: API Design
Breaking: No

Location

• cmd/thv-operator/api/v1alpha1/virtualmcpserver_types.go:475-480

Problem

// EmbeddingServerRef is set but optimizer is not configured: auto-populate
// optimizer with default values so the embedding server is actually used.
if hasRef && !hasOptimizer {
    r.Spec.Config.Optimizer = &config.OptimizerConfig{}
}

This mutation inside a Validate() method:

1. Is never persisted to the API server (the controller doesn't write back to spec)
2. Is re-applied every reconciliation from a fresh cache copy
3. Is invisible to users via kubectl get

Impact

• Violation of separation of concerns (validation should not mutate)
• Users see a different spec than what the controller uses
• If webhooks are implemented, this logic would need to be a Defaulter, not a Validator

Recommended Fix

1. Extract to a separate ApplyDefaults() method or a proper Default() webhook
2. Call ApplyDefaults() before Validate() in the controller
3. Document that the defaulting is controller-side only

Start in cmd/thv-operator/api/v1alpha1/virtualmcpserver_types.go:475-480 and inspect validateEmbeddingServer and the controller path that calls validation. Separate the defaulting step from validation, invoke it before Validate, and verify the relevant operator/API tests pass while the existing embedding-server behavior is preserved.