fix(browser): inject snippets into exec_code context; fix(ui): step order starts at 1 in run detail

- BrowserService.exec() now builds snippet map via SnippetService and passes
  it to CodeExecutorService.execute() for both named-session and anonymous paths
- SnippetModule added to BrowserModule imports to wire the dependency
- RunDetailPage step order column renders s.order + 1 (was 0-based)

client/src/pages/run/RunDetailPage.tsx

@@ -154,7 +154,7 @@ export function RunDetailPage() {
   }, [id, runId]);
 
   const stepColumns: TableColumn<ScenarioRunStep>[] = [
-    { key: 'order', header: t('runs.step_order'), render: (s) => s.order, width: 50 },
+    { key: 'order', header: t('runs.step_order'), render: (s) => s.order + 1, width: 50 },
     {
       key: 'title',
       header: t('runs.step_title'),