feat!: URI-based proof payload locations with blob publication verification

[mfw78]

• Proof { string[] uris; bytes32[] blobVersionedHashes } replaces the numeric location registry: URI mirrors are opaque on-chain; every listed blob hash is verified attached to the transaction via blobhash() (BlobNotAttached) — publication atomic with authorization
• setRoot(bytes32(0)) is an explicit clear and requires an empty proof (ProofDataMalformed)
• normative leafEncoding: "v1" tree-construction vectors: independent implementation verified against the exact MerkleProof.verify check _auth performs, including odd-promotion levels (note: the Murky test helper zero-pads odd nodes — _auth-valid but not the payload standard, which is exactly why the construction is pinned)

BREAKING: setRoot/setRootWithContext signatures and MerkleRootSet topic0 change.

Issues

Closes #33.

Part of #1.

[github-actions]

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