fix(update): accept custom types from types.custom config (GH#hq-8hif1z)

The `bd update --type` command was rejecting custom types (like role, agent,
rig) even when configured via types.custom. The issue was that type validation
used IsValid() which only checks the 5 core types, ignoring custom types.

Changes:
- CLI (update.go): Use IsValidWithCustom() with types from config
- Storage (validators.go): Add validateIssueTypeWithCustom() function
- Storage (queries.go, transaction.go): Fetch and pass custom types

The error message now dynamically shows all valid types including custom ones.

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

internal/storage/sqlite/queries.go

@@ -887,12 +887,11 @@ func (s *SQLiteStorage) UpdateIssue(ctx context.Context, id string, updates map[
 		return fmt.Errorf("issue %s not found", id)
 	}
 
-	// Fetch custom statuses and types for validation
+	// Fetch custom statuses and types for validation (GH#hq-8hif1z)
 	customStatuses, err := s.GetCustomStatuses(ctx)
 	if err != nil {
 		return wrapDBError("get custom statuses", err)
 	}
-
 	customTypes, err := s.GetCustomTypes(ctx)
 	if err != nil {
 		return wrapDBError("get custom types", err)