feat(control-plane): show active Network Validators on the dashboard

[flo2517]

Summary

Contained slice of #29 / ADR-011's dashboard bullet: validator count and list.

Scope, and why it stops here

The full ADR-011 dashboard requirement is "validator count, challenge outcomes, score history, and degraded quorum." This PR ships the count/list honestly. The rest — challenge outcomes, score history, degraded-quorum-per-round — needs reading pallet-network-validator's Rounds/Evidence StorageNMap, which requires correctly replicating Substrate's Blake2_128Concat/Twox64Concat multi-key hashing for a 3-key map. That's real additional risk to get right blind — this sandbox has no live chain to verify decoding against — so it's deliberately left for a follow-up rather than shipped half-verified.

What's here

internal/blockchainbridge/networkvalidator.go: reads pallet-network-validator's ActiveValidatorSet (a StorageValue, so only a fixed twox128(pallet)+twox128(item) key — no per-entry hashing needed) and SCALE-decodes the compact-prefixed Vec<AccountId32> it holds. Adds a decodeCompactUint counterpart to the existing compactUint encoder (registrar.go) and round-trips every mode (single-byte, two-byte, four-byte, big-integer) against it in tests — a subtly wrong decode would silently misread real validator counts rather than error, so this is exactly the kind of logic that needs a real round-trip test, not just "it compiles."

dashboard.go: ValidatorsActive is -1 on a failed read, never 0 — ADR-011's own requirement that a degraded observation must not read as false success applies here as much as to any on-chain state. A pinned JSON-contract test guards the sentinel against a refactor silently dropping it back to Go's int zero value. index.html/app.js render the same distinction: — for unavailable, the real count (including a genuine 0) otherwise.

Verification

$ go build ./...
$ go vet ./...
$ gofmt -l .
$ go test ./...

Full suite green, including 6 new blockchainbridge SCALE-decode tests and the dashboard JSON-contract test.

🤖 Generated with Claude Code