When a component schema uses allOf with a single element (e.g., nullable: true + type: object + allOf: [single item]), the allOf() fast path in gen/schema_gen_sum.go returned the inner schema directly, losing the outer schema's Ref field. This caused the type to be registered as anonymous instead of ref-keyed, leading to anonymous type name conflict errors when the same schema was referenced across multiple operations.

The multi-element allOf path already preserves Ref via mergedSchema.Ref = schema.Ref, but the single-element fast path skipped this.

Fixes #1651

Likely fixed by PR:

• #1448 — anonymous type name conflict: "OptSecretConfig" at tstorage.merge — exact same error path and root cause (single-element allOf losing Ref)
• #1488 — OptError not generated for recursive schema with single-element allOf: [$ref] + nullable: true — this is the same single-element allOf fast path bug; the inner schema loses Ref identity

Fix

Copy the outer schema's Ref onto the inner schema (via shallow copy) before generating, so the type is registered under the correct reference key and reused by subsequent operations.

Reproduction

A schema like:

Bar:
  nullable: true
  type: object
  allOf:
    - type: object
      properties:
        value:
          type: number

referenced from a parent schema used in two operations, once directly, once inside another allOf merge, would fail with: anonymous type name conflict: "Bar"

Test plan

• Added positive test case to _testdata/positive/allOf.yml reproducing the collision pattern
• Added integration test in internal/integration/all_of_test.go (getFoo / getAdminFoo)
• go test . -run TestGenerate/Positive/allOf passes
• go test ./internal/integration -run TestAllof passes
• go test ./gen/... — all existing tests pass
• go test . -run TestGenerate — all positive/negative/example specs pass