refactor: replace wildcard match arms with explicit enum variants

[zmanian]

Motivation

Closes #10211

Wildcard match arms (_ =>) silently swallow new enum variants, which can hide bugs when new variants are added. Replacing them with explicit variant listings ensures the compiler flags any match that needs updating.

Solution

• Replaced all _ => patterns across 42 files with explicit enum variant listings
• Feature-gated variants (ReadResponse::TransactionId behind indexer, Transaction::V6 behind nu7/tx_v6, NetworkUpgrade::ZFuture behind zfuture) handled with #[cfg] arms
• halo2::plonk::Error retains wildcard with #[allow(clippy::wildcard_enum_match_arm)] due to upstream #[non_exhaustive]
• Added indexer feature propagation from zebrad -> zebra-rpc -> zebra-state
• Fixed pre-existing println! clippy lint in zebra-state/src/service/read/tests/vectors.rs (changed to tracing::warn!)

Verification

• cargo fmt --all -- --check passes
• cargo clippy --workspace --all-targets -- -D warnings passes (default features)
• cargo clippy --workspace --all-targets --features indexer -- -D warnings passes

AI Disclosure

Used Claude Code for initial enumeration of wildcard patterns and mechanical replacement. All changes were reviewed and verified by the contributor.

[zmanian]

@conradoplg This is ready for review — CI workflows need maintainer approval to run (fork PR). Could you approve the Actions runs when you get a chance? Thanks!

[Copilot]

Copilot reviewed 41 out of 41 changed files in this pull request and generated no comments.

[oxarbitrage]

Thanks for working on this @zmanian — the refactor aligns with #10211 and conradoplg's acknowledgment there.

I did a detailed review of commit f8f812d5d8. The approach is correct — all the replacements are mechanical, no behavior changes, and the #[non_exhaustive] cases (halo2::plonk::Error, std::io::ErrorKind, ValidateContextError) are properly handled with #[allow] annotations. Nice work.

Two issues to fix and a rebase needed before we can merge:

Bug 1 — Missing Transaction::V6 cfg arms in tests (8 sites)

The non-test code correctly includes the cfg-gated V6 arm, but these test files don't:

• zebra-consensus/src/transaction/tests.rs (4 sites)
• zebra-state/src/service/check/tests/anchors.rs (3 sites)
• zebrad/src/components/mempool/storage/tests/prop.rs (2 sites)

Each needs:

#[cfg(all(zcash_unstable = "nu7", feature = "tx_v6"))]
Transaction::V6 { .. } => // same body as the other arms

Without this, the build breaks under --features tx_v6 with zcash_unstable = "nu7".

Bug 2 — Missing NetworkUpgrade::ZFuture cfg arms (2 sites)

• zebra-rpc/src/methods/types/get_block_template/proposal.rs
• zebrad/tests/acceptance.rs

Each needs:

#[cfg(zcash_unstable = "zfuture")]
NetworkUpgrade::ZFuture => // same body as the other arms

Rebase needed

The branch has 6 commits but only f8f812d5d8 is the actual change — the rest are merge commits and unrelated work. Could you rebase onto current main with just that single commit? You'll hit 3 conflicts:

• zebra-state/src/service/read/tests/vectors.rs — trivial, capitalization change in a tracing::warn!
• zebra-network/src/peer/connection/tests/vectors.rs — trivial, panic format string was updated on main
• zebra-rpc/src/methods.rs — moderate, main restructured the getrawtransaction handler with caller_block_context. Your explicit enum variants need to be placed into the new code flow.

Timing note: This PR touches files that overlap with other in-flight work, so we may need to coordinate merge timing. Getting the rebase and fixes done now means it's ready when the window opens.