fix(galoisd): correct signature/validator count check in Poll

[bit2swaz]

fixes #5428

Summary

both Poll implementations had two input-validation guards comparing each commit's Signatures slice length against itself, so the condition was always false and the "More signatures than validators" error never fired.
a malformed request with more signatures than validators would skip the check entirely and reach the prover. this fixes both comparisons to use Validators on the right-hand side. the same copy paste bug was in both server files; both are patched in this commit

Changes

• galoisd/grpc/server.go: compare Signatures against Validators for both the trusted and untrusted commits
• galoisd/grpc/bls12381_server.go: same fix (the guard was copy pasted from server.go with the same typo)
• galoisd/grpc/server_test.go: regression test that Poll rejects a commit with more signatures than validators, covering both server types and both commit fields (4 sub-cases total)

Testing

go test ./grpc/... in galoisd\. the new test fails before the fix (the dead guard is skipped so a zero-value server hits the job-slot check and returns busy_building), and passes after. also ran go build ./grpc/... and go vet ./grpc/...

[vercel]

@bit2swaz is attempting to deploy a commit to the unionbuild Team on Vercel.

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[bit2swaz]

@benluelo any chances i can get a review on this PR?

[benluelo]

you need to remove the merge commit and rebase your pr off of main instead

[bit2swaz]

rebased. i hope this works :)