fix(chat): honor new-chat intent from secondary pages

Create a fresh local consultation for explicit new-chat navigation and keep reserved recovery from taking over its landing. Add regression tests and record validation gaps for remote review.

Co-Authored-By: Claude Code <noreply@anthropic.com>

frontend/DESIGN.md

@@ -456,6 +456,17 @@ one skeleton, none of them carrying the sidebar.
   `/?c=<uuid>`; the footer is a link to `/`. Renaming, pinning, archiving and
   deleting stay on `/`, backed by `Home()`'s optimistic-update and rollback
   layer, which is far more than these four routes need.
+- **New chat is not a home link.** The read-only 新建对话 action links to
+  `/?new=1`; Home consumes that intent before activation and opens a fresh local
+  consultation. It clears `new`, any `c`, and the login-return stub. Before the
+  first question there is no saved session, no `?c=`, and no new history row.
+  The first question uses the existing persistence flow. A reserved older
+  consultation keeps recovering in the background without taking over this
+  explicit new-chat landing or leaving its startup recovery notice there.
+  The account footer
+  still links to `/`, and a bare-home refresh keeps its existing landing rule.
+  The same action and mobile drawer-close behavior are retained; no extra
+  button, copy, loading state, or visual treatment is introduced.
 - **Leaving the chat is a navigation, not a reload.** 星盘 / 星历 / 我的报告 are
   `AppLink` on every page, including `/`, where they used to be a full document
   load that threw away the React tree, the session list and the account. Only