fix: 添加 goalState 模块存根，修复 CI 构建打包解析失败

CI 中的 autonomy-lifecycle-user-flow 集成测试会执行 build.ts 打包 CLI。
此前 PromptInputFooterLeftSide.tsx 中 require('../../services/goal/goalState.js')
的路径在源码中不存在，打包器报 Could not resolve，导致 (unnamed) 测试失败。

新增 src/services/goal/goalState.ts 存根模块（getGoal 返回 null，组件不渲染），
让打包器在构建期可以解析该 require 路径。同时把 PromptInputFooterLeftSide.tsx
里两处 as unknown as 内联类型签名换成 as typeof import(...)，让类型直接来自
存根模块，避免类型定义重复。

src/components/PromptInput/PromptInputFooterLeftSide.tsx

@@ -137,10 +137,7 @@ function GoalElapsedIndicator(): React.ReactNode {
   }, []);
   void tick;
 
-  const goalModule = require('../../services/goal/goalState.js') as unknown as {
-    getGoal: () => { status: string; [k: string]: unknown } | null;
-    getActiveElapsedMs: (g: { status: string; [k: string]: unknown }) => number;
-  };
+  const goalModule = require('../../services/goal/goalState.js') as typeof import('../../services/goal/goalState');
   const goal = goalModule.getGoal();
   if (!goal) return null;
 
@@ -431,7 +428,7 @@ function ModeIndicator({
       : []),
     // Goal elapsed indicator — compact "goal (XhYmin)" after PID
     ...(feature('GOAL') &&
-    (require('../../services/goal/goalState.js') as unknown as { getGoal: () => unknown }).getGoal()
+    (require('../../services/goal/goalState.js') as typeof import('../../services/goal/goalState')).getGoal()
       ? [<GoalElapsedIndicator key="goal-elapsed" />]
       : []),
   ];

src/services/goal/goalState.ts

@@ -0,0 +1,30 @@
+/**
+ * Stub for the goal feature module.
+ *
+ * The goal feature is not yet implemented. This stub exists so that
+ * PromptInputFooterLeftSide.tsx's require() can be resolved by Bun's
+ * bundler (build.ts). At runtime, getGoal() returns null, so the
+ * GoalElapsedIndicator component renders nothing.
+ *
+ * When the goal feature is implemented, replace this stub with the
+ * real implementation.
+ */
+
+export type GoalState = {
+  status:
+    | 'active'
+    | 'paused'
+    | 'budget_limited'
+    | 'usage_limited'
+    | 'blocked'
+    | 'complete'
+  [key: string]: unknown
+}
+
+export function getGoal(): GoalState | null {
+  return null
+}
+
+export function getActiveElapsedMs(_goal: GoalState): number {
+  return 0
+}