fix: make tests resilient to project .beads/redirect

Tests were failing because beads.FindDatabasePath() follows the
project's .beads/redirect file, causing tests to find unexpected
databases. Fixed by:

- Setting BEADS_DIR in tests that need isolation from git repo detection
- Clearing BEADS_DIR in TestMain to prevent global contamination
- Updating migration test schema to include owner column

This ensures tests work correctly in crew directories that have
redirect files pointing to shared .beads directories.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Executed-By: beads/crew/dave
Rig: beads
Role: crew

internal/syncbranch/syncbranch_test.go

@@ -3,6 +3,7 @@ package syncbranch
 import (
 	"context"
 	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 
@@ -439,6 +440,18 @@ func TestIsConfiguredWithDB(t *testing.T) {
 		tmpDir, _ := os.MkdirTemp("", "test-no-beads-*")
 		defer os.RemoveAll(tmpDir)
 
+		// Set BEADS_DIR to a nonexistent path to prevent git repo detection
+		// from finding the project's .beads directory
+		origBeadsDir := os.Getenv("BEADS_DIR")
+		os.Setenv("BEADS_DIR", filepath.Join(tmpDir, ".beads"))
+		defer func() {
+			if origBeadsDir != "" {
+				os.Setenv("BEADS_DIR", origBeadsDir)
+			} else {
+				os.Unsetenv("BEADS_DIR")
+			}
+		}()
+
 		origWd, _ := os.Getwd()
 		os.Chdir(tmpDir)
 		defer os.Chdir(origWd)