feat: route staged scene skills through runtime

Add registry-driven scene routing and multi-root skill loading so fault-details and 95598 scene skills can be triggered from natural language while still running through the browser-backed runtime.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/compat_cron_test.rs

@@ -17,7 +17,7 @@ async fn compat_cron_adapter_creates_lists_and_runs_due_agent_jobs() {
         api_key: "key".to_string(),
         base_url: "https://api.deepseek.com".to_string(),
         model: "deepseek-chat".to_string(),
-        skills_dir: None,
+        skills_dir: Vec::new(),
     };
     let workspace_root = workspace_root("sgclaw-cron");
     let config = build_zeroclaw_config_from_settings(Path::new(&workspace_root), &settings);