Followups: `NFT refactor -> replace pk with sk #469`

⚪ Nitpicks

1. Witness naming convention — camelCase (https://github.com/OpenZeppelin/compact-contracts/pull/469) NonFungibleToken.compact:137 — Rename wit_NonFungibleTokenSK() → wit_nonFungibleTokenSK(). If agreed, apply consistently to the rest of the refactors.

🔵 Followups

1. Move `` to a utility module (https://github.com/OpenZeppelin/compact-contracts/pull/469) NonFungibleToken.compact:145
2. **Redundant canonicalization in **`` (https://github.com/OpenZeppelin/compact-contracts/pull/469) NonFungibleToken.compact:549 — `canonOwner`/`canonSpender` are canonicalized, then `isApprovedForAll(canonOwner, canonSpender)` re-canonicalizes them at L391–392. Same pattern in `_update` line 615 where `fromAddress` (already canonical, sourced from `_ownerOf`) is re-canonicalized.
3. Move helper to a separate module (https://github.com/OpenZeppelin/compact-contracts/pull/469) NonFungibleToken.compact:924
4. Move helper to Utils (https://github.com/OpenZeppelin/compact-contracts/pull/469) NonFungibleToken.compact:935
5. Test hasher drift risk (https://github.com/OpenZeppelin/compact-contracts/pull/469) contracts/src/token/test/nonFungibleToken.test.ts:14 — Fine for now, but if the hasher in the circuit changes, this fn must change too. Worth adding a note on the function.
6. **Drop redundant **** calls in ** (https://github.com/OpenZeppelin/compact-contracts/pull/469) NonFungibleToken.compact:612–617
   • L612: _isTargetZero(disclose(fromAddress)) → _isTargetZero(fromAddress)
   • L616: _balances.lookup(disclose(canonFrom)) → _balances.lookup(canonFrom)
   • L617: _balances.insert(disclose(canonFrom), disclose(newBalance)) → _balances.insert(canonFrom, newBalance)
     Rationale: fromAddress = _ownerOf(tokenId) is a ledger read (untainted), canonFrom inherits that, lookup - 1 stays untainted. Cross-cutting: worth running the same audit on the merged FT / AC / Ownable refactors.

Start with the referenced NonFungibleToken.compact locations and contracts/src/token/test/nonFungibleToken.test.ts, then review PR #469 for the surrounding refactor context. Resolve the listed naming, utility-module, canonicalization, disclosure, and test-maintenance followups, and audit the merged FT, AC, and Ownable refactors for the same redundant calls.