cmd/ghash: production genesis block-0 hash verifier (evm/geth-v1.20.1)

Computes core.Genesis.ToBlock().Hash() on the maintained EVM path, replacing
the legacy coreth-based state/cmd verifiers (which no longer build against the
current stack). Used to close the mainnet regenesis launch gate: canonical
genesis/configs/mainnet/cchain.json and the deployed k8s cChainGenesis both
compute 0x3f4fa2a0...ec61e (== RLP block-0), state root 0x2d1cedac.

Co-authored-by: Hanzo Dev <[email protected]>

cmd/ghash/main.go

@@ -0,0 +1,37 @@
+// Command ghash computes the canonical block-0 hash of one or more C-Chain
+// genesis JSON files via luxfi/evm core.Genesis.ToBlock — the production path
+// (geth v1.20.1), replacing the legacy coreth-based verifier.
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+
+	"github.com/luxfi/evm/core"
+)
+
+func hashOf(path string) (out string) {
+	defer func() {
+		if r := recover(); r != nil {
+			out = fmt.Sprintf("panic: %v", r)
+		}
+	}()
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return fmt.Sprintf("read error: %v", err)
+	}
+	var g core.Genesis
+	if err := json.Unmarshal(data, &g); err != nil {
+		return fmt.Sprintf("unmarshal error: %v", err)
+	}
+	b := g.ToBlock()
+	return fmt.Sprintf("block-0 = %s  (allocs=%d ts=0x%x skipPMF=%v)",
+		b.Hash().Hex(), len(g.Alloc), g.Timestamp, g.SkipPostMergeFields)
+}
+
+func main() {
+	for _, path := range os.Args[1:] {
+		fmt.Printf("%s\n  %s\n", path, hashOf(path))
+	}
+}