step 2: init command + SQLite storage + migrations + config

- storage.go: DB wrapper, migration runner (in-code SQL strings)
- migrations.go: 001_init (nodes + node_meta + indexes)
- vault.go: Init() creates .verstak/ dirs, config.yml, index.db
- config.go: YAML config read/write
- util/uuid.go: UUIDv7 generator
- cmd/verstak/main.go: init --vault PATH command
- main_test.go: TestInitCreatesVault, TestInitConfigYAML

Acceptance: go build ./... pass, go test ./... pass
Init creates test-vault with .verstak/index.db + config.yml
Repeat Init is safe.

cmd/verstak/main.go

@@ -3,6 +3,9 @@ package main
 import (
 	"fmt"
 	"os"
+	"path/filepath"
+
+	"verstak/internal/core/vault"
 )
 
 const version = "0.1.0-dev"
@@ -17,18 +20,49 @@ func main() {
 	case "--version", "-v":
 		fmt.Println("Verstak", version)
 	case "--help", "-h":
-		fmt.Println("Verstak — local-first working vault")
-		fmt.Println()
-		fmt.Println("Usage: verstak <command> [flags]")
-		fmt.Println()
-		fmt.Println("Commands:")
-		fmt.Println("    init      Initialize a new vault")
-		fmt.Println("    --version Show version")
-		fmt.Println("    --help    Show this help")
+		usage()
 	case "init":
-		fmt.Println("TODO: init command (step 2)")
+		runInit()
 	default:
 		fmt.Fprintf(os.Stderr, "Unknown command: %s\n", os.Args[1])
 		os.Exit(1)
 	}
 }
+
+func usage() {
+	fmt.Println("Verstak — local-first working vault")
+	fmt.Println()
+	fmt.Println("Usage: verstak <command> [flags]")
+	fmt.Println()
+	fmt.Println("Commands:")
+	fmt.Println("    init --vault PATH    Initialize a new vault at PATH")
+	fmt.Println("    --version            Show version")
+	fmt.Println("    --help               Show this help")
+}
+
+func runInit() {
+	vaultPath := "."
+	// Parse --vault flag
+	for i := 2; i < len(os.Args); i++ {
+		if os.Args[i] == "--vault" && i+1 < len(os.Args) {
+			vaultPath = os.Args[i+1]
+			break
+		}
+	}
+
+	abs, err := filepath.Abs(vaultPath)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		os.Exit(1)
+	}
+
+	if err := vault.Init(abs); err != nil {
+		fmt.Fprintf(os.Stderr, "Init failed: %v\n", err)
+		os.Exit(1)
+	}
+
+	fmt.Println("Vault initialized at", abs)
+	fmt.Println("  .verstak/index.db")
+	fmt.Println("  .verstak/config.yml")
+	fmt.Println("  spaces/")
+}

cmd/verstak/main_test.go

@@ -0,0 +1,81 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"verstak/internal/core/storage"
+	"verstak/internal/core/vault"
+)
+
+func TestInitCreatesVault(t *testing.T) {
+	dir := t.TempDir()
+	vaultPath := filepath.Join(dir, "test-vault")
+
+	if err := vault.Init(vaultPath); err != nil {
+		t.Fatalf("Init failed: %v", err)
+	}
+
+	// Check directories exist.
+	for _, sub := range []string{".verstak", ".verstak/trash", ".verstak/history",
+		".verstak/originals", ".verstak/thumbnails", ".verstak/blobs", "spaces"} {
+		p := filepath.Join(vaultPath, sub)
+		if _, err := os.Stat(p); os.IsNotExist(err) {
+			t.Errorf("missing: %s", p)
+		}
+	}
+
+	// Check index.db exists and is a valid SQLite database.
+	dbPath := filepath.Join(vaultPath, ".verstak", "index.db")
+	db, err := storage.Open(dbPath)
+	if err != nil {
+		t.Fatalf("open db: %v", err)
+	}
+	defer db.Close()
+
+	var count int
+	if err := db.QueryRow("SELECT COUNT(*) FROM nodes").Scan(&count); err != nil {
+		t.Fatalf("query nodes: %v", err)
+	}
+	if count != 0 {
+		t.Errorf("expected 0 nodes, got %d", count)
+	}
+
+	// Idempotent: second Init should not fail.
+	if err := vault.Init(vaultPath); err != nil {
+		t.Fatalf("second Init failed: %v", err)
+	}
+}
+
+func TestInitConfigYAML(t *testing.T) {
+	dir := t.TempDir()
+	vaultPath := filepath.Join(dir, "vault")
+
+	if err := vault.Init(vaultPath); err != nil {
+		t.Fatalf("Init: %v", err)
+	}
+
+	cfgPath := filepath.Join(vaultPath, ".verstak", "config.yml")
+	data, err := os.ReadFile(cfgPath)
+	if err != nil {
+		t.Fatalf("read config: %v", err)
+	}
+
+	if len(data) == 0 {
+		t.Fatal("config.yml empty")
+	}
+	// yaml key should be present.
+	if !containsString(string(data), "engine:") {
+		t.Errorf("config missing engine key:\n%s", string(data))
+	}
+}
+
+func containsString(s, sub string) bool {
+	for i := 0; i+len(sub) <= len(s); i++ {
+		if s[i:i+len(sub)] == sub {
+			return true
+		}
+	}
+	return false
+}