fix(web): 无用户行钉顶、闲置不上留白，并修会话列表 tsc 两错

frontend/src/hooks/use-conversation-scroll-anchor.ts

@@ -76,9 +76,26 @@ export function applyFollowBottom(
   element.scrollTop = element.scrollHeight;
 }
 
+export function lastTurnTail(container: HTMLElement): HTMLElement | null {
+  return (container.querySelector(".message-list > :last-child .message-assistant")
+    ?? container.querySelector(".message-assistant:last-of-type")
+    ?? container.querySelector(".message-user:last-of-type")) as HTMLElement | null;
+}
+
+export function turnHeadHeightForSpacer(head: HTMLElement | null, tail: HTMLElement | null): number {
+  if (!head) return 0;
+  // The last assistant carries the min-height spacer. Measuring it as the turn
+  // head feeds the spacer back into itself (BUG-931).
+  if (tail && head === tail) return 0;
+  return head.offsetHeight;
+}
+
 export function applyTurnSpacer(container: HTMLElement, head: HTMLElement | null): void {
   container.style.setProperty("--conversation-viewport", `${container.clientHeight}px`);
-  container.style.setProperty("--latest-turn-head-height", `${head?.offsetHeight ?? 0}px`);
+  container.style.setProperty(
+    "--latest-turn-head-height",
+    `${turnHeadHeightForSpacer(head, lastTurnTail(container))}px`,
+  );
 }
 
 export function clearTurnSpacer(container: HTMLElement): void {
@@ -86,12 +103,6 @@ export function clearTurnSpacer(container: HTMLElement): void {
   container.style.removeProperty("--latest-turn-head-height");
 }
 
-export function lastTurnTail(container: HTMLElement): HTMLElement | null {
-  return (container.querySelector(".message-list > :last-child .message-assistant")
-    ?? container.querySelector(".message-assistant:last-of-type")
-    ?? container.querySelector(".message-user:last-of-type")) as HTMLElement | null;
-}
-
 export function turnTailOverflow(container: HTMLElement): number {
   const last = lastTurnTail(container);
   if (!last) return conversationDistanceFromBottom(container);
@@ -198,8 +209,8 @@ export function useConversationScrollAnchor(
       }
       if (anchoredRef.current) {
         element.scrollTop = element.scrollHeight;
-      } else {
-        applyTurnSpacer(element, pinnedHeadRef.current ?? resolveTurnHead(element));
+      } else if (pinnedHeadRef.current) {
+        applyTurnSpacer(element, pinnedHeadRef.current);
       }
       setLatestBelowFold(latestContentBelowFold(turnTailOverflow(element)));
     };
@@ -240,7 +251,9 @@ export function useConversationScrollAnchor(
       const element = container.current;
       holdUnpin.current = false;
       shouldLand.current = false;
+      pinnedHeadRef.current = null;
       if (element) {
+        clearTurnSpacer(element);
         const reduceMotion = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
         element.scrollTo({ top: element.scrollHeight, behavior: reduceMotion ? "auto" : "smooth" });
         setLatestBelowFold(false);

frontend/src/lib/session-sidebar-row.ts

@@ -27,7 +27,7 @@ export function toSidebarSessionRow(
 ): SidebarSession {
   return {
     id: session.id,
-    title: sessionSidebarTitle(session, library),
+    title: sessionSidebarTitle(session),
     subtitle: sessionSidebarSubtitle(session, library) || null,
     pinned: session.pinned,
     archived: Boolean(session.archivedAt),