Add NU6.2 Zaino support

[czarcas7ic]

Summary

Adds NU6.2-capable Zaino/Zebra dependencies to Zallet and points the workspace at the Valar Zaino branch with NU6.2 activation support. That Zaino pin uses the Valar zingo_common_components fork so NU6.2 activation heights round trip instead of being dropped.

This targets the wallet base branch that already contains z_shieldcoinbase, so the combined branch can be used to test the transparent coinbase payout path with Zebra, Zaino, and Zallet. It uses the Valar zcash_script 0.4.5 backport commit for the libzcash_script build-script fix instead of vendoring the crate into this repo.

It also pins the old Orchard/Halo2 sources needed by the zcashd import dependency so the CI job that deletes Cargo.lock can still resolve dependencies from a clean checkout.

Known CI

• cargo-vet needs audit metadata for the newly introduced NU6.2 Zebra/Zaino dependency stack before this can merge.
• The integration-test trigger fails in this fork because the GitHub App token inputs are not present.

Test plan

• cargo update -p zaino-common -p zaino-fetch -p zaino-proto -p zaino-state -p libzcash_script -p zcash_script -p zingo_common_components
• cargo update -p orchard@0.10.2
• cargo update -p halo2_gadgets@0.3.1 --precise 0.3.0
• cargo fmt --all -- --check
• cargo check -p zallet --tests
• git diff --check
• temporarily remove Cargo.lock and run cargo generate-lockfile, then restore the committed lockfile

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	zebra-chain@​2.0.0 ⏵ 9.0.0	-18	+75
	zebra-rpc@​2.0.1 ⏵ 9.0.0	+3	+2			+31
	futures@​0.3.31 ⏵ 0.3.32
	zebra-state@​2.0.0 ⏵ 8.0.0

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