core: 补全 state 容器初始化与实体访问接口

docs/min_core_draft/README.org

@@ -57,7 +57,7 @@ wm_workspace_t *ws = &state->workspaces[workspace_id];  // O(1)
 wm_output_t *output = &state->outputs[output_id];      // O(1)
 
 // 动态实体：线性查找（简单且足够）
-wm_window_t *win = wm_state_find_window(state, window_id);  // O(n)
+const wm_window_t *win = wm_state_window_get(state, window_id);  // O(n)
 ```
 
 **设计优势**：

docs/min_core_draft/WM_EVENT_ROUTING.org

@@ -53,27 +53,23 @@ void runtime_handle_metadata_event(wm_runtime_t *runtime, const wm_event_t *even
     const wm_window_metadata_changed_event_t *e = &event->as.window_metadata_changed;
 
     // 1. 查找窗口
-    wm_window_t *win = wm_state_find_window(&runtime->state, e->window_id);
+    const wm_window_t *win = wm_state_window_get(&runtime->state, e->window_id);
     if (!win) {
         return;  // 窗口已被销毁
     }
 
-    // 2. 直接更新窗口元数据字段
+    // 2. 通过 state 接口更新窗口元数据字段
     if (e->changed_fields & WM_WINDOW_META_CHANGED_TITLE) {
-        free(win->title);
-        win->title = e->title ? strdup(e->title) : NULL;
+        wm_state_window_set_title(&runtime->state, e->window_id, e->title);
     }
     if (e->changed_fields & WM_WINDOW_META_CHANGED_APP_ID) {
-        free(win->app_id);
-        win->app_id = e->app_id ? strdup(e->app_id) : NULL;
+        wm_state_window_set_app_id(&runtime->state, e->window_id, e->app_id);
     }
     if (e->changed_fields & WM_WINDOW_META_CHANGED_CLASS) {
-        free(win->class_name);
-        win->class_name = e->class_name ? strdup(e->class_name) : NULL;
+        wm_state_window_set_class(&runtime->state, e->window_id, e->class_name);
     }
     if (e->changed_fields & WM_WINDOW_META_CHANGED_INSTANCE) {
-        free(win->instance_name);
-        win->instance_name = e->instance_name ? strdup(e->instance_name) : NULL;
+        wm_state_window_set_instance(&runtime->state, e->window_id, e->instance_name);
     }
 
     // 3. 标记 render 脏（状态栏需要更新）

docs/min_core_draft/WM_POLICY_APPLY_COMMAND_SKELETON.org

@@ -177,7 +177,7 @@ static bool apply_manage_window(wm_state_t *state,
   wm_window_id_t id = command->as.manage_window.window_id;
   wm_workspace_id_t ws_id = command->as.manage_window.workspace_id;
 
-  if (wm_state_find_window_const(state, id)) return false;
+  if (wm_state_window_get(state, id)) return false;
   wm_workspace_t *ws = require_workspace(state, ws_id);
   if (!ws) return false;