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/src/lib/chat-session-url.ts

@@ -1,4 +1,5 @@
 export const SESSION_URL_QUERY_KEY = "c";
+export const NEW_CHAT_QUERY_KEY = "new";
 export const SESSION_URL_RETURN_STORAGE_KEY = "jyotisha.session-url-return";
 export const SESSION_MISSING_NOTICE = "该对话不存在或已被删除";
 export const SESSION_LOOKUP_FAILED_NOTICE = "这条对话暂时读不到，请稍后重试。";
@@ -11,11 +12,20 @@ export type SessionUrlQuery = {
 
 export type BootstrapSessionSelection = {
   readonly sessionId: string;
-  readonly urlAction: "keep" | "replace-selected" | "replace-clear" | "none" | "lookup";
+  readonly urlAction: "keep" | "replace-selected" | "replace-clear" | "none" | "lookup" | "new-chat";
   readonly missing: boolean;
   readonly clearStoredReturn: boolean;
 };
 
+export function newChatHref(): string {
+  return "/?new=1";
+}
+
+export function parseNewChatIntent(search: string): boolean {
+  const params = new URLSearchParams(search.startsWith("?") ? search.slice(1) : search);
+  return params.has(NEW_CHAT_QUERY_KEY);
+}
+
 export function parseSessionUrlQuery(search: string): SessionUrlQuery {
   const params = new URLSearchParams(search.startsWith("?") ? search.slice(1) : search);
   if (!params.has(SESSION_URL_QUERY_KEY)) {
@@ -30,6 +40,7 @@ export function parseSessionUrlQuery(search: string): SessionUrlQuery {
 
 export function sessionHref(search: string, sessionId: string | null, pathname = "/"): string {
   const params = new URLSearchParams(search.startsWith("?") ? search.slice(1) : search);
+  params.delete(NEW_CHAT_QUERY_KEY);
   if (sessionId) params.set(SESSION_URL_QUERY_KEY, sessionId);
   else params.delete(SESSION_URL_QUERY_KEY);
   const query = params.toString();
@@ -79,6 +90,14 @@ export function resolveBootstrapSessionSelection(input: {
   readonly search: string;
   readonly storedReturnId: string | null;
 }): BootstrapSessionSelection {
+  if (parseNewChatIntent(input.search)) {
+    return {
+      sessionId: input.defaultSessionId,
+      urlAction: "new-chat",
+      missing: false,
+      clearStoredReturn: true,
+    };
+  }
   const query = parseSessionUrlQuery(input.search);
   if (query.present) {
     if (query.sessionId && input.listedIds.includes(query.sessionId)) {

frontend/src/lib/home-bootstrap.ts

@@ -18,7 +18,7 @@ export type LandingSession = Readonly<{
   messages: readonly unknown[];
 }>;
 
-export type LandingUrlAction = "keep" | "replace-selected" | "replace-clear" | "none" | "lookup";
+export type LandingUrlAction = "keep" | "replace-selected" | "replace-clear" | "none" | "lookup" | "new-chat";
 
 /**
  * A rectification Case is opened only when the address bar names that session
@@ -43,7 +43,7 @@ export function resolveStarterHomeLandingSessionId(
   selectedId: string,
   urlAction: LandingUrlAction,
 ): string {
-  if (urlAction === "keep" || urlAction === "replace-selected" || urlAction === "lookup") {
+  if (urlAction === "keep" || urlAction === "replace-selected" || urlAction === "lookup" || urlAction === "new-chat") {
     return selectedId;
   }
   const selected = sessions.find((session) => session.id === selectedId);
@@ -61,6 +61,7 @@ export function starterHomeLandingNeedsConsultation(
   landingId: string,
   urlAction: LandingUrlAction,
 ): boolean {
+  if (urlAction === "new-chat") return true;
   if (urlAction === "keep" || urlAction === "replace-selected" || urlAction === "lookup") return false;
   const landing = sessions.find((session) => session.id === landingId);
   return !landing || landing.sessionType === "birth_time_rectification";