Add bd migrate command for database upgrades (bd-164)

- Implement bd migrate command with detection, version checking, and cleanup
- Update daemon to suggest bd migrate for version mismatches
- Enhance CLI version warnings to recommend bd migrate
- Add comprehensive tests for migration scenarios
- Document migration workflow in QUICKSTART.md and AGENTS.md

Completes bd-164 and epic bd-159

Amp-Thread-ID: https://ampcode.com/threads/T-34ea4682-8c48-44c2-8421-dc40f867773b
Co-authored-by: Amp <amp@ampcode.com>

cmd/bd/migrate_test.go

@@ -0,0 +1,127 @@
+package main
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/steveyegge/beads/internal/storage/sqlite"
+)
+
+func TestMigrateCommand(t *testing.T) {
+	// Create temporary test directory
+	tmpDir := t.TempDir()
+	beadsDir := filepath.Join(tmpDir, ".beads")
+	if err := os.MkdirAll(beadsDir, 0750); err != nil {
+		t.Fatalf("Failed to create .beads directory: %v", err)
+	}
+
+	t.Run("no databases", func(t *testing.T) {
+		databases, err := detectDatabases(beadsDir)
+		if err != nil {
+			t.Fatalf("detectDatabases failed: %v", err)
+		}
+		if len(databases) != 0 {
+			t.Errorf("Expected 0 databases, got %d", len(databases))
+		}
+	})
+
+	t.Run("single old database", func(t *testing.T) {
+		// Create old database
+		oldDBPath := filepath.Join(beadsDir, "vc.db")
+		store, err := sqlite.New(oldDBPath)
+		if err != nil {
+			t.Fatalf("Failed to create old database: %v", err)
+		}
+
+		// Set old version
+		ctx := context.Background()
+		if err := store.SetMetadata(ctx, "bd_version", "0.16.0"); err != nil {
+			t.Fatalf("Failed to set old version: %v", err)
+		}
+		_ = store.Close()
+
+		// Detect databases
+		databases, err := detectDatabases(beadsDir)
+		if err != nil {
+			t.Fatalf("detectDatabases failed: %v", err)
+		}
+		if len(databases) != 1 {
+			t.Fatalf("Expected 1 database, got %d", len(databases))
+		}
+		if databases[0].version != "0.16.0" {
+			t.Errorf("Expected version 0.16.0, got %s", databases[0].version)
+		}
+
+		// Migrate to beads.db
+		targetPath := filepath.Join(beadsDir, "beads.db")
+		if err := os.Rename(oldDBPath, targetPath); err != nil {
+			t.Fatalf("Failed to migrate database: %v", err)
+		}
+
+		// Verify migration
+		databases, err = detectDatabases(beadsDir)
+		if err != nil {
+			t.Fatalf("detectDatabases failed after migration: %v", err)
+		}
+		if len(databases) != 1 {
+			t.Fatalf("Expected 1 database after migration, got %d", len(databases))
+		}
+		if filepath.Base(databases[0].path) != "beads.db" {
+			t.Errorf("Expected beads.db, got %s", filepath.Base(databases[0].path))
+		}
+	})
+
+	t.Run("version detection", func(t *testing.T) {
+		// Test getDBVersion with beads.db from previous test
+		dbPath := filepath.Join(beadsDir, "beads.db")
+		version := getDBVersion(dbPath)
+		if version != "0.16.0" {
+			t.Errorf("Expected version 0.16.0, got %s", version)
+		}
+
+		// Update version
+		store, err := sqlite.New(dbPath)
+		if err != nil {
+			t.Fatalf("Failed to open database: %v", err)
+		}
+		ctx := context.Background()
+		if err := store.SetMetadata(ctx, "bd_version", Version); err != nil {
+			t.Fatalf("Failed to update version: %v", err)
+		}
+		_ = store.Close()
+
+		// Verify updated version
+		version = getDBVersion(dbPath)
+		if version != Version {
+			t.Errorf("Expected version %s, got %s", Version, version)
+		}
+	})
+}
+
+func TestFormatDBList(t *testing.T) {
+	dbs := []*dbInfo{
+		{path: "/tmp/.beads/beads.db", version: "0.17.5"},
+		{path: "/tmp/.beads/old.db", version: "0.16.0"},
+	}
+
+	result := formatDBList(dbs)
+	if len(result) != 2 {
+		t.Fatalf("Expected 2 results, got %d", len(result))
+	}
+
+	if result[0]["name"] != "beads.db" {
+		t.Errorf("Expected name beads.db, got %s", result[0]["name"])
+	}
+	if result[0]["version"] != "0.17.5" {
+		t.Errorf("Expected version 0.17.5, got %s", result[0]["version"])
+	}
+
+	if result[1]["name"] != "old.db" {
+		t.Errorf("Expected name old.db, got %s", result[1]["name"])
+	}
+	if result[1]["version"] != "0.16.0" {
+		t.Errorf("Expected version 0.16.0, got %s", result[1]["version"])
+	}
+}