fix(ferriskey): clear two clippy lib errors blocking every matrix job

[avifenesh]

Summary

cargo clippy -- -D warnings fails on main inside the vendored ferriskey lib. Because the scoped workspace clippy job compiles ferriskey as a dependency, all three clippy invocations fail — and with them every valkey N · standalone|cluster matrix leg.

Location	Lint	Fix
ferriskey/src/cluster/routing.rs:552	clippy::for_kv_map	for (_, arg_indices) in routes.iter_mut() → routes.values_mut()
ferriskey/src/cmd.rs:74	clippy::question_mark	collapse if-let/else-return into self.cmd.cursor?

The cmd.rs change is the idiom the surrounding code already uses — next_item returns Option<T> and calls ? on the next two lines, so this is consistent rather than a new style.

Pre-existing, not a regression

Verified on a clean checkout of main @ 0def596 with zero local changes — identical two errors. This debt is what's been failing the matrix; it isn't introduced by any dependency PR.

Verification — all three CI clippy invocations now exit 0

cargo clippy -p ff-core -p ff-script -p ff-engine -p ff-scheduler \
  -p ff-sdk -p ff-server -p ff-test -p ff-backend-sqlite \
  --features ff-sdk/direct-valkey-claim -- -D warnings   # exit 0
cargo clippy -p ferriskey --all-targets -- -D warnings              # exit 0
cargo clippy -p ferriskey --all-targets --features iam -- -D warnings  # exit 0

Scope note

Two files, 3 insertions / 6 deletions. Deliberately not bundled with #532 (the RUSTSEC lockfile sweep) so the security fix stays reviewable as a lockfile-only diff.

While confirming this I also found ~35 further clippy errors in test files (result_large_err in parity_stage_c/d1, needless_range_loop across flow_edge_policies_stage_*). Those are invisible to CI today because the scoped clippy job runs without --all-targets — only ferriskey gets the all-targets treatment. Left out of this PR; worth a separate cleanup pass, and possibly worth deciding whether the workspace job should gain --all-targets to stop that drift recurring.

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[gemini-code-assist]

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[avifenesh]

Absorbed into #534 alongside the security lockfile update, avoiding a merge with known baseline audit failures.