refactor(policy): 删除 action 模块，将 action -> command 解析放在 policy 模块内部

- 删除 src/core/action.c|h，将 spawn 移至 src/base/process
- policy_resolve_action 实现完整的 action 分发逻辑
- binding_table_cycle_mode 改为纯计算，返回模式 ID 而非修改状态
- 从 state 移除 state_workspace_cycle_layout / state_cycle_current_output
- 新增 ZDWM_COMMAND_QUIT 命令，通过 plan 标志驱动 runtime 退出
- set_binding_mode 现在生成 BIND_KEY effect 以同步后端按键绑定
- 扩展 action 数据类型支持 window_send_to_workspace 和 window_cycle_output

src/core/binding.c

@@ -231,8 +231,11 @@ bool binding_table_set_current_mode(
   return true;
 }
 
-bool binding_table_cycle_mode(binding_table_t *table, int delta) {
-  if (!table || !table->modes || table->count < 1) return false;
+zdwm_binding_mode_id_t
+binding_table_cycle_mode(const binding_table_t *table, int32_t delta) {
+  if (!table || !table->modes || table->count <= 1) {
+    return ZDWM_BINDING_MODE_ID_INVALID;
+  }
 
   bool matched = false;
   size_t index = (size_t)table->current_mode;
@@ -248,17 +251,13 @@ bool binding_table_cycle_mode(binding_table_t *table, int delta) {
     }
   }
 
-  if (!matched) return false;
-
-  /* 只有一个模式没必要切换 */
-  if (table->count == 1) return true;
+  if (!matched) return ZDWM_BINDING_MODE_ID_INVALID;
 
   int64_t count      = (int64_t)table->count;
   int64_t next_index = ((int64_t)index + (int64_t)delta) % count;
   if (next_index < 0) next_index += count;
-  table->current_mode = table->modes[next_index].id;
 
-  return true;
+  return table->modes[next_index].id;
 }
 
 const key_binding_t *