fix(web): 四个页面共用一份会话列表，空会话不入列

对话、星盘、星历、报告进同一 (app) 外壳，列表只拉一次。服务端不再列出空咨询；新建复用已有空会话。新标题改成「生时校正 · M月D日」，侧栏副标题用创建时间。

frontend/tests/session-conversation-layout.test.ts

@@ -16,7 +16,7 @@ test("aligns the session transcript and composer to one readable column", () =>
 });
 
 test("keeps onboarding transcript and intake card on the same session column", () => {
-  const pageSource = readProjectFile("src/app/page.tsx");
+  const pageSource = readProjectFile("src/app/(app)/page.tsx");
   assert.match(pageSource, /\$\{!profileComplete \? " is-onboarding" : ""\}/);
   assert.match(globalStyles, /\.conversation\.is-onboarding \.welcome \{[\s\S]*width:\s*min\(calc\(var\(--session-column-width\) \+ \(var\(--session-column-gutter\) \* 2\)\), 100%\)/);
   assert.match(globalStyles, /\.conversation\.is-onboarding\.is-empty \.welcome \{[\s\S]*width:\s*min\(var\(--session-column-width\), 100%\)/);
@@ -25,7 +25,7 @@ test("keeps onboarding transcript and intake card on the same session column", (
 });
 
 test("centers the starter home even when the conversation grid is not is-empty", () => {
-  const pageSource = readProjectFile("src/app/page.tsx");
+  const pageSource = readProjectFile("src/app/(app)/page.tsx");
   // 原值：空态 `.welcome` 与 `.starter-list` 都是 1040px
   // 新值：`.welcome` 收到 `--session-column-width`，`.starter-list` 已删
   // 原因：空态输入框此前 1040px、会话态 760px，首条消息落地时输入框会当场变窄一截。