fix(agent): 输入草稿按会话保留,切换会话、关抽屉不丢

会话面板与新对话输入框的草稿原来是组件内状态,切到别的会话或 Esc 关抽屉就没了。
改为按会话(以及列表页 / 抽屉两处新对话)分键记在模块里,发送成功后清掉。

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Cxwgnn2pbzQ7rXv3rq7fei

apps/web/app/components/agent/agent-nav.ts

@@ -108,3 +108,20 @@ export function usePageListGroup(activeRun?: AgentRunGroup | null): [AgentRunGro
     );
   return [group, change];
 }
+
+// ── 输入草稿:按会话(和两处新对话输入框)分开记,切换会话、关抽屉不丢;发送成功后清掉。模块级,刷新页面才清 ──
+
+const drafts = new Map<string, string>();
+export const DRAFT_PAGE_GOAL = "goal:page";
+export const DRAFT_DRAWER_GOAL = "goal:drawer";
+export const runDraftKey = (runId: string) => `run:${runId}`;
+
+export function readDraft(key: string | undefined): string {
+  return key ? (drafts.get(key) ?? "") : "";
+}
+
+export function writeDraft(key: string | undefined, text: string): void {
+  if (!key) return;
+  if (text.trim()) drafts.set(key, text);
+  else drafts.delete(key);
+}