[BUG] Default ORT EF leaked in embedded CreateCollection for existing collections

[tazarov]

Description

When CreateCollection is called with CreateIfNotExists=true (i.e. via GetOrCreateCollection) and the collection already exists (isNewCreation=false), PrepareAndValidateCollectionRequest() unconditionally creates a default ORT EmbeddingFunction that holds native ONNX Runtime resources (session handles, environment state).

The isNewCreation=false path then sets overrideEF = nil and overrideContentEF = nil, discarding the reference to the default ORT EF without ever closing it. The EF is never stored in collection state or passed to a collection constructor, so its Close() is never called.

Impact

Every call to GetOrCreateCollection on the embedded client for an already-existing collection leaks one ORT EmbeddingFunction's native ONNX resources. Over many calls this accumulates leaked session handles and environment state.

Affected code

• pkg/api/v2/client_local_embedded.go: CreateCollection lines 347, 408-411
• pkg/api/v2/client.go: PrepareAndValidateCollectionRequest lines 274-284 (where default ORT EF is created)

Notes

• Pre-existing since commit 843cab5 (Feb 2026), not introduced by PR feat: add contentEmbeddingFunction support to GetOrCreateCollection #491
• Identified during review of PR feat: add contentEmbeddingFunction support to GetOrCreateCollection #491
• Possible fix: close the default EF when isNewCreation=false before discarding it:

  } else {
      if closer, ok := req.embeddingFunction.(io.Closer); ok {
          _ = closer.Close()
      }
      overrideEF = nil
      overrideContentEF = nil
  }