ZEC Harness: Upgrade to NU6.1 (zcashd v6.11.0)

[dev-warrior777]

This PR updates the ZEC regtest harness to support NU6.1, enabling testing of the DEX wallet integration with the latest Zcash protocol.

Key Changes

• NU6.1 activation: Added nuparams=c8e71055:5 and nuparams=4dec4df0:7 (ZIP 253/255)
• Transparent addresses: Switched from z_getaddressforaccount → getnewaddress (deprecated in v6+)
• Regtest compatibility: Added -allowdeprecated=getnewaddress
• Robustness: fixed sendtoaddress spacing
• All nodes activated: NU6.1 params now on alpha, beta, delta, gamma

Why

• zcashd v6.11.0 defaults to unified addresses and account 0 behavior
• DEX harness uses transparent UTXOs → must use getnewaddress
• Without these, go test fails with "account not found" or empty UTXOs

Tested

./harness.sh
./beta getbalance   # → 74.00000000

[dev-warrior777]

Notes:

Current NU6.1 wallets are recreated on each run

• need to export to dex/testing/zec
• uncomment wallet import logic in the script

Test: go test -v -tags=harness -run=TestWallet ./client/asset/zec - still fails

• likely needs a regtest specific switch (avoid using common code)

Same upgrades to daemon startup applied to loadbot issue #3378

• untested

NU5 -> NU6.1 - More research needed:

• Account 0 behavior has changed
• Unified address APIs are default
• many RPC's are removed and/or deprecated

[dev-warrior777]

Issue #3470

Need to upgrade again for v6.11.0.

Zcashd seems to have a limited lifetime as they transition to Zebrad/Zallet which is already on mainnet.

Zcash Roadmap - `Zcashd` End-of-Service

Zebra (zebrad) Mainnet Status

Current Availability: Zebra is already operational on the Zcash mainnet. As of January 9, 2026, the most current stable release is Zebra 3.1.0 (released December 19, 2025).
Feature Status: Zebra 3.1.0 supports the latest NU6.1 network upgrade and includes production-ready features such as enhanced spam filters and ARM compatibility.
Deprecation Timeline: The Zcash ecosystem is in a critical migration window. The legacy zcashd software has an "End-of-Service" (EOS) milestone on January 21, 2026. After this, the network will increasingly rely on zebrad for full-node consensus. 

Zallet Development Status

Purpose: Zallet is being developed as a modern, high-performance replacement for the legacy zcashd wallet.
Release Date: A specific mainnet launch date for Zallet has not yet been disclosed.
Recent Activity: Following the mass resignation of the Electric Coin Company (ECC) team on January 8, 2026, the departing members (led by Josh Swihart) announced they are forming a new company to build a new Zcash wallet. It is unclear if this new effort will merge with or replace the existing Zallet project. 

Summary of Key 2026 Milestones

Milestone Estimated Date Status
======== ============= =====
zcashd End-of-Service January 21, 2026 Legacy node phase-out *
Shielded Swaps (NEAR) Q1 2026 Private cross-chain swaps
Ztarknet L2 Mainnet Mid-2026 Layer-2 smart contracts
NU7 Network Upgrade September 2026 Potential protocol upgrade **

Notes:

1. Can upgrade to Zcashd v6.11.0 on this PR and change title - Or a new PR after this one.
2. Saw some info on net about Zcashd becoming unresponsive after this update (maybe 16 weeks but unclear)
3. If we want to add Zebrad/Zallet - Full Node then we should start now for continuity. Alternatively we could start looking at the (unfinished) Zingo Labs Zingo lite wallet which is written in rust. Zingo is on GitHub and we would 'drive' with the recommended gRPC, I guess .. not 100% sure.

[dev-warrior777]

Changing wiki always gives conflict.

[JoeGruffins]

Will review asap.

[dev-warrior777]

Need to make it better ..