feat(ui): 星盘/星历/报告中心并入 app 外壳，侧栏不再消失

三个页面此前各是脱离外壳的独立全屏路由，各写了一套一样的
*-shell / *-topbar（只有一个「返回对话」链接）/ *-hero 骨架，
侧栏在打开它们的瞬间整个消失。

新增 AppNavRail（只读：两个 GET，零写操作）与 SecondaryShell。
会话行走 sessionHref → /?c=<uuid>，跳转复用现有侧栏的
persistLoginSessionReturn + location.assign，行为完全一致。

刻意不带重命名/收藏/归档/删除与账户菜单：那套连着 Home() 的乐观更新与
回滚层，为四个路由把它整体上提远超需要，且会撞 useState 增长门禁。

四个路由渲染标记完全不变：/ ○、/chart ○、/ephemeris ○、/reports ƒ。
CSS gzip 39,825→39,727（−0.25%）；per-route JS 体积构建不输出，
已作为口径缺口记录。

两处自身问题被测试抓到并修复：usePathname() 在 app-router 上下文外
返回 null（类型说是 string）、fetch 在 jsdom 里可能不存在。
另差点随 hero 一起丢掉 BUG-717 的 eyebrow 文案（成本与速度承诺，
会印在失败页上），已放回 tab 行下方。

/reports/[reportId] 留给 R6 与目录一起做；根边界页保留「返回对话」，
它们不得 import globals.css，挂不了外壳。

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0193vBv6w5MV2cifdTUu9H5P

frontend/src/hooks/use-nav-rail.ts

@@ -0,0 +1,116 @@
+"use client";
+
+import { useEffect, useState } from "react";
+
+/**
+ * Read-only nav data for the secondary pages (/chart, /ephemeris, /reports).
+ *
+ * The chat page's sidebar is fed by `Home()`'s hooks, which also own renaming,
+ * deleting, pinning and archiving — optimistic updates, confirmation dialogs and
+ * rollback included. Lifting that whole layer so four routes can share it is far
+ * more than these pages need: none of them offers session management. Two GETs
+ * are enough, and this hook never writes.
+ */
+
+export type NavRailSession = {
+  readonly id: string;
+  readonly title: string;
+  readonly pinned: boolean;
+  readonly updatedAt: number;
+};
+
+export type NavRailAccount = {
+  readonly name: string;
+  readonly initial: string;
+  readonly credits: number;
+};
+
+export type NavRailState = {
+  readonly sessions: readonly NavRailSession[];
+  readonly account: NavRailAccount | null;
+  /** True once both requests have settled, however they settled. */
+  readonly settled: boolean;
+  /** The viewer is not signed in; the rail degrades to brand plus a login link. */
+  readonly signedOut: boolean;
+};
+
+type SessionRow = {
+  id?: unknown;
+  title?: unknown;
+  pinned?: unknown;
+  updated_at?: unknown;
+};
+
+function toSession(row: SessionRow): NavRailSession | null {
+  if (typeof row.id !== "string" || !row.id) return null;
+  const updatedAt = typeof row.updated_at === "string" ? Date.parse(row.updated_at) : Number.NaN;
+  return {
+    id: row.id,
+    title: typeof row.title === "string" && row.title.trim() ? row.title.trim() : "新对话",
+    pinned: row.pinned === true,
+    updatedAt: Number.isFinite(updatedAt) ? updatedAt : 0,
+  };
+}
+
+export function useNavRail(): NavRailState {
+  const [sessions, setSessions] = useState<readonly NavRailSession[]>([]);
+  const [account, setAccount] = useState<NavRailAccount | null>(null);
+  const [settled, setSettled] = useState(false);
+  const [signedOut, setSignedOut] = useState(false);
+
+  useEffect(() => {
+    const controller = new AbortController();
+    let cancelled = false;
+
+    async function load() {
+      if (typeof fetch !== "function") {
+        setSettled(true);
+        return;
+      }
+      const [sessionResult, accountResult] = await Promise.allSettled([
+        fetch("/api/sessions?limit=40", { signal: controller.signal }),
+        fetch("/api/account", { signal: controller.signal }),
+      ]);
+      if (cancelled) return;
+
+      if (sessionResult.status === "fulfilled" && sessionResult.value.ok) {
+        const body = await sessionResult.value.json().catch(() => null) as { sessions?: unknown } | null;
+        const rows = Array.isArray(body?.sessions) ? body.sessions as SessionRow[] : [];
+        if (!cancelled) setSessions(rows.map(toSession).filter((item): item is NavRailSession => item !== null));
+      } else if (sessionResult.status === "fulfilled" && sessionResult.value.status === 401) {
+        if (!cancelled) setSignedOut(true);
+      }
+
+      if (accountResult.status === "fulfilled" && accountResult.value.ok) {
+        const body = await accountResult.value.json().catch(() => null) as {
+          credits?: unknown;
+          user?: { email?: unknown };
+          profile?: { name?: unknown };
+        } | null;
+        const name = typeof body?.profile?.name === "string" ? body.profile.name.trim() : "";
+        const email = typeof body?.user?.email === "string" ? body.user.email : "";
+        if (!cancelled) {
+          setAccount({
+            name: name || email || "账户",
+            initial: name.slice(0, 1) || email.slice(0, 1).toUpperCase() || "你",
+            credits: typeof body?.credits === "number" ? body.credits : 0,
+          });
+        }
+      } else if (accountResult.status === "fulfilled" && accountResult.value.status === 401) {
+        if (!cancelled) setSignedOut(true);
+      }
+
+      if (!cancelled) setSettled(true);
+    }
+
+    void load().catch(() => {
+      if (!cancelled) setSettled(true);
+    });
+    return () => {
+      cancelled = true;
+      controller.abort();
+    };
+  }, []);
+
+  return { sessions, account, settled, signedOut };
+}