Adds the confidential mint/burn path to the /confidential subpath, which today ships InstructionPlan helpers for transfer, withdraw and configure but nothing for ConfidentialMintBurn — leaving downstream consumers to re-derive the three-proof orchestration themselves.

Supersedes #1338, which I closed after mistakenly agreeing it duplicated #1253. It does not: #1253 added the fee-aware transfer path (TransferFeeConfig + ConfidentialTransferFee, five proofs, U256 range), and contains no ConfidentialMintBurn handling. This PR is rebased onto main now that #1253 has landed, and builds on its primitives rather than re-introducing its own.

What's added

• getConfidentialMintInstructionPlan / getConfidentialBurnInstructionPlan — build the equality, batched grouped-3-handles validity and U128 range proofs, verify them via context-state accounts, and assemble the token instruction, reusing the existing transfer/withdraw plumbing (buildContextStateProofPlan).
• getPermissionedConfidentialBurnInstructionPlan — the permissioned burn variant. token-2022 rejects the standard ConfidentialBurn on mints carrying the PermissionedBurn extension, so this is required for those mints. Identical proofs; the mint's configured permissionedBurnAuthority co-signs alongside the account owner.
• getUpdateConfidentialMintBurnDecryptableSupplyInstructionFromSupply — re-encrypts the decryptable supply under the supply AES key. The ElGamal supply and the AES decryptable supply can drift (e.g. ApplyPendingBurn advances the former but cannot re-encrypt the latter), so the authority uses this to re-assert it.
• addWithLoHiCiphertexts in confidentialTransferArithmetic.ts — the one missing arithmetic primitive, mirroring the existing subtractWithLoHiCiphertexts, for homomorphically adding the minted amount to the encrypted supply.

Reusing #1253's primitives

#1338 and #1253 both incidentally grew their own copies of two small helpers. Rather than reintroduce mine, this PR adopts #1253's and converges the file on one of each:

• Mint-extension lookup — dropped my getRequiredConfidentialMintBurnExtension for getRequiredMintExtension(mintAccount, 'ConfidentialMintBurn'). While there, getRequiredConfidentialTransferMintExtension folds into the same generic, since that is what the generic was written to replace.
• Auditor resolution — dropped my resolveAuditorElGamalPubkey and widened the existing async getAuditorElGamalPubkey to a structural input, so transfer, transfer-with-fee, mint and burn all resolve the auditor key through one function. This keeps the fetch-the-mint fallback rather than my version's zero-pubkey fallback, which would have silently produced proofs the program rejects for a mint with a configured auditor.
• u64 guards — dropped my local U64_MAX comparisons for assertU64Amount. assertMintBurnAmount stays: its 2^48−1 bound is specific to the lo/hi split used for the mint/burn range proof and has no analogue in the fee path.

The mint/burn input types compose ConfidentialTransferContextStateProofMode for payer/rpc/proofMode, matching the transfer inputs, instead of redeclaring them.

Testing

• test/confidentialTransferArithmetic.test.ts — offline check that addWithLoHiCiphertexts matches a plaintext add.
• test/extensions/confidentialMintBurn/getConfidentialMintBurnInstructionPlan.test.ts — validator e2e: mint → apply → burn → apply-pending-burn → update-supply against the on-chain ZK verifiers.
• test/extensions/confidentialMintBurn/getPermissionedConfidentialBurnInstructionPlan.test.ts — confidential burn on a PermissionedBurn mint.

Full suite green against a local validator (76 files / 149 tests), including #1253's transfer-with-fee test — worth noting since the auditor resolver is now shared by every proof path. tsc --noEmit, pnpm lint and pnpm format clean.