refactor: remove ws-only scene routing remnants

Keep the ws branch focused on websocket and Zhihu behavior by dropping staged scene-routing artifacts and restoring single-path skills dir semantics.

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

src/runtime/mod.rs

@@ -1,14 +1,9 @@
 mod engine;
 mod profile;
-mod scene_registry;
 mod tool_policy;
 
 pub use engine::{
     is_zhihu_hotlist_task, is_zhihu_write_task, task_requests_zhihu_article_publish, RuntimeEngine,
 };
 pub use profile::RuntimeProfile;
-pub use scene_registry::{
-    load_first_slice_scene_registry, load_scene_registry_from_root, match_scene_instruction,
-    match_scene_instruction_in_registry, DispatchMode, SceneRegistryEntry,
-};
 pub use tool_policy::ToolPolicy;