chore(antd): cut v0.6.0-rc.1 — bump ant-core to 0.2.3, evmlib to 0.8.1

Pulls in the latest stable ant-client (ant-cli-v0.2.2 tag, ant-core 0.2.3)
and the merkle-fix evmlib 0.8.1 — resolves wave-batch external-signer
mainnet payments per the prior investigation.

Cargo.lock simplifies considerably (saorsa-core/transport minor bumps,
ant-node no longer pulled as a build dep).

CI gate verified locally: fmt, clippy -D warnings, doc, test (19 pass).

Public-upload visibility work intentionally deferred from this rc; not
yet mainnet-validated. Release candidate; do not push the v0.6.0-rc.1
tag until review.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Nic-dorman