feat(schema): Update schema of engine_getBlobsV2 as per Osaka.md

[swastik7805]

Closes #777

Fix: Align engine_getBlobsV2 result schema with Osaka spec

Problem

The result schema for engine_getBlobsV2 in blob.yaml only declares an array return type. As per osaka.md, the method must return null whenever any requested blob is missing, pruned, or unavailable — making null a primary return value, not an edge case.

The current schema does not permit null, creating a mismatch between the machine-readable spec and the Markdown specification.

Change

Updated the result schema in blob.yaml to use oneOf, allowing eitheran array of BlobAndProofV2 objects or null.

Fix

result:
  name: List of blobs and corresponding cell proofs
  schema:
    oneOf:
      - type: array
        items:
          $ref: '#/components/schemas/BlobAndProofV2'
      - type: 'null'

References

• osaka.md — engine_getBlobsV2
• blob.yaml#L50

@MysticRyuujin please review the issue and PR