fix: derive Nexus EIP-712 domain version fallback from MEE version

[fichiokaku]

Summary

`NEXUS_DOMAIN_VERSION` is a static `"1.2.0"` string (Constants.ts:110) that's only correct for MEE versions backed by Nexus 1.2.0 (`V2_0_0`, `V2_1_0`). For any MEE `≥ V2_2_0` the Nexus domain version moved to the 1.3.x line, so the hardcoded constant produces signatures the on-chain Nexus contract rejects.

The bug surfaces in:

• `getAccountMeta`'s fallback path — taken when `eip712Domain()` cannot be queried on-chain (e.g. for a counterfactual SCA whose factory isn't deployed yet).
• `makeInstallDataAndHash`'s default `domainVersion` parameter.

Neither has production call sites in abstractjs (only tests + external consumers), so the runtime impact of this release is zero — this is a correctness fix for downstream users and a safer default for any future internal use.

What's added

A small helper `getNexusDomainVersion(meeVersionOrConfig)` that derives the correct version from the existing `MEEVersionConfig.accountId` field. The `accountId` is already formatted as `biconomy.nexus.<X.Y.Z>` and mirrors the on-chain `_domainNameAndVersion()` return — no new mapping is needed; abstractjs already has this data per MEE version in `DEFAULT_CONFIGURATIONS_BY_MEE_VERSION`.

```ts
getNexusDomainVersion(MEEVersion.V2_2_2) // → "1.3.2"
getNexusDomainVersion(MEEVersion.V2_2_1) // → "1.3.1"
getNexusDomainVersion(MEEVersion.V2_1_0) // → "1.2.0"
getNexusDomainVersion(getMEEVersion(MEEVersion.V2_2_2)) // → "1.3.2"
```

What's changed

File	Change
`src/sdk/constants/index.ts`	Add `getNexusDomainVersion` helper
`src/sdk/account/utils/Utils.ts`	`getAccountMeta` gains an optional 3rd parameter `meeVersionOrConfig`; when supplied the fallback derives from it. Backwards-compatible — existing two-arg call sites still hit the legacy fallback. `makeInstallDataAndHash` docstring updated to point at the new helper.
`src/sdk/account/utils/Constants.ts`	`NEXUS_DOMAIN_VERSION` marked `@deprecated` with migration guidance. Constant still exported for back-compat.

Why this matters

The production signing path in `signQuote.ts` already uses viem's `getEip712Domain` action which queries on-chain correctly, so the bug does not affect already-deployed accounts signed via the standard flow. Where it surfaces:

1. Counterfactual SCA flows that need the domain version before `eip712Domain()` is queryable.
2. External consumers importing `NEXUS_DOMAIN_VERSION` directly or calling `getAccountMeta` without overriding.
3. Smart Session install-mode flows built on top of `makeInstallDataAndHash` that don't pass an explicit `domainVersion`.

Test plan

• `bunx tsc --noEmit` clean — 0 errors
• Existing tests pass on CI
• Optional: add a unit test asserting `getNexusDomainVersion(MEEVersion.V2_2_2) === "1.3.2"` for each enum entry (kept out of this PR to keep scope tight — happy to add as a follow-up)

---

PR-Codex overview

This PR focuses on updating the handling of the Nexus EIP-712 domain version, introducing a new method for determining the correct version based on the MEE version, and deprecating the legacy constant.

Detailed summary

• Added documentation for NEXUS_DOMAIN_VERSION indicating its deprecation.
• Introduced getNexusDomainVersion function for determining the domain version based on MEE version.
• Updated makeInstallDataAndHash to default to NEXUS_DOMAIN_NAME and warn about legacy version.
• Enhanced getAccountMeta to use getNexusDomainVersion for determining the version if MEE version is provided.

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[github-actions]

size-limit report 📦

Path	Size
core (esm)	71.97 KB (+0.02% 🔺)
core (cjs)	87.18 KB (+0.25% 🔺)
bundler (tree-shaking)	7.15 KB (+0.17% 🔺)
paymaster (tree-shaking)	543 B (0%)