Test or narrow the supported viem version range

[ryley-o]

Problem

ABX packages declare a broad viem range beginning at ^2.21.0, but the repository does not test clean consumers at the declared boundary or across later allowed releases. An allowed version can therefore introduce type incompatibilities without CI noticing.

Desired outcome

Make the declared compatibility range an executable claim.

Acceptance criteria

• Add clean-consumer typecheck coverage at the minimum supported version and a current allowed version, or narrow the declared range to what is actually supported.
• Cover the public SDK types as consumed outside the workspace, not only source builds using the repository lockfile.
• Document the supported range consistently across published packages.