chore(ts): drop dead Plonk VK scaffolding and port #22655 TS cleanup

[AztecBot]

Context

Follow-up to #22655 (feat!: poseidon2 with compressed internal rounds and aux wires) and the scope audit that started from it.

The original PR surfaced a recurring pain: every time the MegaHonk flavor changes, TypeScript has to be hand-edited because several downstream call sites duplicate derived VK sizes or freeze entire VKs as inline blobs. While auditing for similar bad patterns, it became clear that a chunk of the stdlib VK module is Plonk-era scaffolding \u2014 pre-Honk types whose only remaining callers are themselves test-only or dead. Those classes are why the flavor-change struggle exists in TS in the first place: VerificationKeyData.makeFakeHonk was synthesising fake keyAsBytes by serializing a fake Plonk VerificationKey, dragging Plonk types into the Honk path.

What this PR does (3 commits)

1. chore(stdlib): remove dead mocked_keys.ts hex blob

Deletes yarn-project/stdlib/src/abi/mocked_keys.ts, a ~2 KB orphan Plonk VK hex blob. Grepping the monorepo: 1 declaration, 0 references. stdlib/src/abi/index.ts does not re-export it.

2. chore(ts): use MEGA_VK_LENGTH_IN_FIELDS instead of hardcoded 4064

Ports the TS-only cleanup from #22655 so it lands independently of whether the Poseidon2 flavor change merges:

• 4 call sites of Buffer.alloc(4064) in aztec.js/src/contract/{contract,deploy_method}.test.ts \u2192 Buffer.alloc(MEGA_VK_LENGTH_IN_FIELDS * Fr.SIZE_IN_BYTES).
• VerificationKey.makeFakeMegaHonk() dropped its ~4 KB base64 blob in favor of Buffer.alloc(MEGA_VK_LENGTH_IN_FIELDS * Fr.SIZE_IN_BYTES).

Intentionally NOT ported: the MEGA_VK_LENGTH_IN_FIELDS 127\u2192135 bump in constants.gen.ts, which tracks the C++ flavor change that's not in merge-train/barretenberg. The ported code is layout-agnostic.

3. chore(stdlib): drop Plonk VerificationKey/CommitmentMap/G1AffineElement

Deletes the entire Plonk-era VK scaffold. Nothing reads it off the wire and nothing in Honk needs it:

• VerificationKey (Plonk class with CommitmentMap of {Q_1, SIGMA_1, ...}, containsRecursiveProof, recursiveProofPublicInputIndices): zero non-test callers. Every caller was itself dead (makeVerificationKey factory, a one-off round-trip test, or the Honk VerificationKeyData fake helpers that were using it as a source of placeholder bytes).
• CommitmentMap and G1AffineElement: only referenced by VerificationKey. Gone.
• CircuitType enum (STANDARD/ULTRA) in stdlib/src/types/shared.ts: only existed to type-tag Plonk VKs. Gone.
• makeVerificationKey in stdlib/src/tests/factories.ts: exported but not imported anywhere.
• 'can deserialize vk built by noir' test: round-tripped an inline ~2 KB Plonk VK hex; cannot parse any current protocol VK.
• VerificationKeyData.makeFakeHonk / makeFakeRollupHonk: now synthesize keyAsBytes from VerificationKeyAsFields.toBuffer() (the real Honk serialization) instead of from a fake Plonk VK. makeFake(len) had zero callers and was removed.
• VerificationKey.makeFakeMegaHonk(): its one remaining caller (pxe/.../private_kernel_execution_prover.test.ts) now inlines Buffer.alloc(MEGA_VK_LENGTH_IN_FIELDS * Fr.SIZE_IN_BYTES).

Net: \u2212209 lines from stdlib/src/vks/verification_key.ts plus the shared / factories / pxe updates.

Scope audit (gist)

https://gist.github.com/AztecBot/67c6cc69458f63c296d0557b2e598632 (updated)

Verification

grep across yarn-project/ confirms zero remaining references to VerificationKey.makeFake, VerificationKey.makeFakeMegaHonk, VerificationKey.fromBuffer, new VerificationKey(, CommitmentMap, G1AffineElement, CircuitType, or makeVerificationKey. Remaining hits for the string VerificationKey are unrelated (VerificationKeyAsFields, VerificationKeyData, PrivateVerificationKeyHints, VerificationKeyNoir type binding, computeVerificationKeyHash, makeProofAndVerificationKey).

[ledwards2225]

Ick! thanks