fix(consult): drop traces, budget checkpoints, silent summary inherit

BUG-729: dropped history rounds leave an omission marker in the model-visible summary slot.
BUG-730: checkpoint threshold is 0.4 of historyBudgetChars (128k still 16,000).
BUG-731: session_full new chat copies owned context_summary on the server; clients send only continued_from_session_id.

frontend/src/hooks/use-consultation-run.ts

@@ -135,7 +135,7 @@ export type ConsultationRunParams = {
   uiPreviewMode: MutableRefObject<string | null>;
   persistSession: (session: ChatSession, mode?: "create" | "update") => Promise<void>;
   updateSession: (sessionId: string, change: (session: ChatSession) => ChatSession) => void;
-  startNewChat: () => Promise<ChatSession | null>;
+  startNewChat: (options?: { continuedFromSessionId?: string }) => Promise<ChatSession | null>;
   continueInNewChat: (prompt: { question: string; theme: Theme }) => Promise<void>;
   refreshAccount: () => Promise<void>;
   openAccountDialog: (dialog: AccountDialog, options?: HTMLButtonElement | null | OpenAccountDialogOptions) => void;

frontend/src/hooks/use-session-management.ts

@@ -139,7 +139,11 @@ export function useSessionManagement(params: SessionManagementParams) {
     setSessions((current) => current.map((session) => (session.id === sessionId ? change(session) : session)));
   }
 
-  async function persistSession(session: ChatSession, mode: "create" | "update" = "update") {
+  async function persistSession(
+    session: ChatSession,
+    mode: "create" | "update" = "update",
+    options?: { continuedFromSessionId?: string },
+  ) {
     if (!account) throw new Error("账户尚未加载完成");
     if (process.env.NODE_ENV === "development" && uiPreview.current) return;
     const values = mode === "create"
@@ -153,6 +157,9 @@ export function useSessionManagement(params: SessionManagementParams) {
         chart_profile_id: session.chartProfileId,
         chart_profile_name: session.chartProfileName,
         chart_profile_role: session.chartProfileRole,
+        ...(options?.continuedFromSessionId
+          ? { continued_from_session_id: options.continuedFromSessionId }
+          : {}),
       }
       : {
         title: session.title,
@@ -192,7 +199,10 @@ export function useSessionManagement(params: SessionManagementParams) {
 
   async function continueInNewChat(prompt: { question: string; theme: Theme }) {
     setSessionFullPrompt(null);
-    const created = await startNewChat();
+    const sourceSessionId = activeSessionId;
+    const created = await startNewChat(
+      sourceSessionId ? { continuedFromSessionId: sourceSessionId } : undefined,
+    );
     if (!created) return;
     setDraft(prompt.question);
     setDraftTheme(prompt.theme);
@@ -294,7 +304,7 @@ export function useSessionManagement(params: SessionManagementParams) {
     }
   }
 
-  async function startNewChat(): Promise<ChatSession | null> {
+  async function startNewChat(options?: { continuedFromSessionId?: string }): Promise<ChatSession | null> {
     if (!account || !modelCatalog || creatingSession) return null;
     const nextSession = {
       ...createSession(modelCatalog.defaultModelId),
@@ -312,7 +322,13 @@ export function useSessionManagement(params: SessionManagementParams) {
     setComposerNotice("");
     setRequestError(null);
     try {
-      await persistSession(nextSession, "create");
+      await persistSession(
+        nextSession,
+        "create",
+        options?.continuedFromSessionId
+          ? { continuedFromSessionId: options.continuedFromSessionId }
+          : undefined,
+      );
       return nextSession;
     } catch (caught) {
       setSessions((current) => current.filter((session) => session.id !== nextSession.id));