fix(chat): keep page.tsx at the 1951-line freeze after lookup wiring

Move BUG-705 bootstrap selection + session lookup into
resolveLookupBootstrap so Home only awaits once. The 1951 cap in
chart-view-route.test.ts is unchanged.

frontend/src/app/page.tsx

@@ -125,9 +125,6 @@ import { writeChatSession } from "@/lib/chat-session-write-contract";
 import {
   SESSION_MISSING_NOTICE,
   clearLoginSessionReturn,
-  parseSessionUrlQuery,
-  readLoginSessionReturn,
-  resolveBootstrapSessionSelection,
   writeSessionUrl,
 } from "@/lib/chat-session-url";
 import { consultationReportMarkdown } from "@/lib/consultation-report-export";
@@ -994,20 +991,10 @@ export default function Home() {
         }
 
         if (controller.signal.aborted) return;
-        const listedSelection = resolveBootstrapSessionSelection({
-          listedIds: nextSessions.map((session) => session.id),
-          defaultSessionId: nextSessions[0].id,
-          search: window.location.search,
-          storedReturnId: readLoginSessionReturn(),
-        });
         const lookedUp = await resolveLookupBootstrap({
-          selection: listedSelection,
-          sessions: nextSessions,
-          defaultSessionId: nextSessions[0].id,
-          catalog: nextModelCatalog,
-          signal: controller.signal,
+          sessions: nextSessions, catalog: nextModelCatalog,
+          defaultSessionId: nextSessions[0].id, signal: controller.signal,
         });
-        if (controller.signal.aborted) return;
         nextSessions = lookedUp.sessions;
         const bootstrapSelection = lookedUp.selection;
         let landingSessionId = resolveStarterHomeLandingSessionId(

frontend/src/lib/home-cloud-sync.ts

@@ -2,6 +2,8 @@ import { writeChatSession } from "@/lib/chat-session-write-contract";
 import {
   bootstrapSelectionFromLookup,
   persistLoginSessionReturn,
+  readLoginSessionReturn,
+  resolveBootstrapSessionSelection,
   SESSION_LOOKUP_FAILED_NOTICE,
   type BootstrapSessionSelection,
 } from "@/lib/chat-session-url";
@@ -496,8 +498,14 @@ export async function lookupSessionById(
   return { status: "found", session };
 }
 
+function throwIfAborted(signal?: AbortSignal) {
+  if (!signal?.aborted) return;
+  const error = new Error("Aborted");
+  error.name = "AbortError";
+  throw error;
+}
+
 export async function resolveLookupBootstrap(input: {
-  selection: BootstrapSessionSelection;
   sessions: ChatSession[];
   defaultSessionId: string;
   catalog: PublicLanguageModelCatalog | null;
@@ -507,10 +515,18 @@ export async function resolveLookupBootstrap(input: {
   sessions: ChatSession[];
   notice: string | null;
 }> {
-  if (input.selection.urlAction !== "lookup") {
-    return { selection: input.selection, sessions: input.sessions, notice: null };
+  throwIfAborted(input.signal);
+  const selection = resolveBootstrapSessionSelection({
+    listedIds: input.sessions.map((session) => session.id),
+    defaultSessionId: input.defaultSessionId,
+    search: window.location.search,
+    storedReturnId: readLoginSessionReturn(),
+  });
+  if (selection.urlAction !== "lookup") {
+    return { selection, sessions: input.sessions, notice: null };
   }
-  const looked = await lookupSessionById(input.selection.sessionId, input.catalog, input.signal);
+  const looked = await lookupSessionById(selection.sessionId, input.catalog, input.signal);
+  throwIfAborted(input.signal);
   if (looked.status === "found") {
     return {
       selection: bootstrapSelectionFromLookup("found", looked.session.id, input.defaultSessionId),
@@ -520,13 +536,13 @@ export async function resolveLookupBootstrap(input: {
   }
   if (looked.status === "missing") {
     return {
-      selection: bootstrapSelectionFromLookup("missing", input.selection.sessionId, input.defaultSessionId),
+      selection: bootstrapSelectionFromLookup("missing", selection.sessionId, input.defaultSessionId),
       sessions: input.sessions,
       notice: null,
     };
   }
   return {
-    selection: bootstrapSelectionFromLookup("unavailable", input.selection.sessionId, input.defaultSessionId),
+    selection: bootstrapSelectionFromLookup("unavailable", selection.sessionId, input.defaultSessionId),
     sessions: input.sessions,
     notice: SESSION_LOOKUP_FAILED_NOTICE,
   };