fix(merkle): use latest available version when exact contractTreeElem…

[es-kt]

…ents version is missing

When totalElements crosses a 32-element batch boundary, contractTreeElements jumps by 32. If the local chairman tree hasn't merged that batch yet (e.g. due to indexer lag or sync gaps), getChairmanMerkleVersion returns undefined for the exact version — causing hybrid mode to silently skip local proof and fall back to the remote freezer service.

Fix: when the exact version is unavailable, fall back to the latest stored version that still covers all requested CIDs. The returned latest_cid is adjusted to match the version actually used, so pickMerkleRootIndex finds the correct on-chain root (its search window already tolerates this offset).

Verified: 12h / 550+ cycles / 356 transfers with zero proof errors on Sepolia testnet, with the remote freezer service completely unreachable.

Summary

Brief description of changes.

Changes

Testing

• pnpm run test passes
• pnpm run build succeeds
• pnpm run type-check passes

Related Issues

Closes #

[gemini-code-assist]

Code Review

This pull request refactors the local Merkle proof generation logic in MerkleEngine to include a fallback mechanism. When the exact contract version is unavailable locally, the engine now attempts to use the latest local version that covers all requested CIDs. It also updates the returned latest_cid to match the version used and refines error reporting to distinguish between missing storage adapters and missing version data. I have no feedback to provide.