fix(chat): address PR review issues for checkpoint navigation

- Revert out-of-scope esbuild.mjs retry logic (separate concern)
- Add "checkpoint-nav" to ScrollFollowDisengageSource union type
- Guard onJumpToPreviousCheckpoint render behind prop check in CheckpointMenu
- Replace arbitrary Tailwind values (mr-[6px]/ml-[6px]) with standard mr-1.5/ml-1.5

webview-ui/src/components/chat/ChatView.tsx

@@ -1426,7 +1426,7 @@ const ChatViewComponent: React.ForwardRefRenderFunction<ChatViewRef, ChatViewPro
 		const nextCheckpointIndex = checkpointIndices[nextCursor]
 		checkpointJumpCursorRef.current = nextCursor
 
-		enterUserBrowsingHistory("keyboard-nav-up")
+		enterUserBrowsingHistory("checkpoint-nav")
 		virtuosoRef.current?.scrollToIndex({
 			index: nextCheckpointIndex,
 			align: "center",
@@ -1687,7 +1687,7 @@ const ChatViewComponent: React.ForwardRefRenderFunction<ChatViewRef, ChatViewPro
 									<StandardTooltip content={t("chat:scrollToBottom")}>
 										<Button
 											variant="secondary"
-											className={hasLatestCheckpoint ? "flex-1 mr-[6px]" : "flex-[2]"}
+											className={hasLatestCheckpoint ? "flex-1 mr-1.5" : "flex-[2]"}
 											onClick={handleScrollToBottomAndResetCheckpointCursor}>
 											<span className="codicon codicon-chevron-down"></span>
 										</Button>
@@ -1696,7 +1696,7 @@ const ChatViewComponent: React.ForwardRefRenderFunction<ChatViewRef, ChatViewPro
 										<StandardTooltip content={t("chat:scrollToLatestCheckpoint")}>
 											<Button
 												variant="secondary"
-												className="flex-1 ml-[6px]"
+												className="flex-1 ml-1.5"
 												onClick={handleScrollToLatestCheckpoint}
 												aria-label={t("chat:scrollToLatestCheckpoint")}>
 												<span className="codicon codicon-history"></span>

webview-ui/src/components/chat/checkpoints/CheckpointMenu.tsx

@@ -172,16 +172,18 @@ export const CheckpointMenu = ({
 					</div>
 				</PopoverContent>
 			</Popover>
-			<StandardTooltip content={t("chat:scrollToLatestCheckpoint")}>
-				<Button
-					variant="ghost"
-					size="icon"
-					onClick={onJumpToPreviousCheckpoint}
-					data-testid="jump-previous-checkpoint-btn"
-					aria-label={t("chat:scrollToLatestCheckpoint")}>
-					<span className="codicon codicon-chevron-up" />
-				</Button>
-			</StandardTooltip>
+			{onJumpToPreviousCheckpoint && (
+				<StandardTooltip content={t("chat:scrollToLatestCheckpoint")}>
+					<Button
+						variant="ghost"
+						size="icon"
+						onClick={onJumpToPreviousCheckpoint}
+						data-testid="jump-previous-checkpoint-btn"
+						aria-label={t("chat:scrollToLatestCheckpoint")}>
+						<span className="codicon codicon-chevron-up" />
+					</Button>
+				</StandardTooltip>
+			)}
 			<Popover open={moreOpen} onOpenChange={(open) => setMoreOpen(open)} data-testid="more-popover">
 				<StandardTooltip content={t("chat:task.seeMore")}>
 					<PopoverTrigger asChild>

webview-ui/src/hooks/useScrollLifecycle.ts

@@ -25,7 +25,12 @@ const HYDRATION_RETRY_WINDOW_MS = 160
 
 export type ScrollPhase = "HYDRATING_PINNED_TO_BOTTOM" | "ANCHORED_FOLLOWING" | "USER_BROWSING_HISTORY"
 
-export type ScrollFollowDisengageSource = "wheel-up" | "row-expansion" | "keyboard-nav-up" | "pointer-scroll-up"
+export type ScrollFollowDisengageSource =
+	| "wheel-up"
+	| "row-expansion"
+	| "keyboard-nav-up"
+	| "pointer-scroll-up"
+	| "checkpoint-nav"
 
 // ---------------------------------------------------------------------------
 // Helpers