fix: ensure checkpoints appear in chat even with invalid metadata

- Modified CheckpointSaved component to show fallback display when checkpoint metadata is missing or invalid
- Added console warnings to help debug checkpoint metadata issues
- Prevents checkpoints from being completely hidden due to schema validation failures
- Fixes issue #5899 where users reported not seeing checkpoints despite having them enabled

The component now:
- Shows a fallback checkpoint display with default metadata when validation fails
- Logs warnings to console for debugging purposes
- Displays "metadata unavailable" indicator when using fallback data
- Ensures CheckpointMenu still functions with fallback metadata

Author: roomote

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

@@ -17,32 +17,55 @@ export const CheckpointSaved = ({ checkpoint, ...props }: CheckpointSavedProps)
 
 	const metadata = useMemo(() => {
 		if (!checkpoint) {
+			console.warn("[CheckpointSaved] No checkpoint metadata provided", { ts: props.ts, commitHash: props.commitHash })
 			return undefined
 		}
 
 		const result = checkpointSchema.safeParse(checkpoint)
 
 		if (!result.success) {
+			console.warn("[CheckpointSaved] Invalid checkpoint metadata", {
+				checkpoint,
+				errors: result.error.errors,
+				ts: props.ts,
+				commitHash: props.commitHash
+			})
 			return undefined
 		}
 
 		return result.data
-	}, [checkpoint])
+	}, [checkpoint, props.ts, props.commitHash])
 
-	if (!metadata) {
-		return null
-	}
+	// Always show the checkpoint, even if metadata is invalid
+	// This ensures users can see that checkpoints are being created
+	const fallbackMetadata = useMemo(() => {
+		if (metadata) {
+			return metadata
+		}
+		
+		// Create fallback metadata when the original is invalid
+		return {
+			isFirst: false, // Default to regular checkpoint
+			from: "", // Empty string as fallback
+			to: props.commitHash, // Use the commit hash we have
+		}
+	}, [metadata, props.commitHash])
 
 	return (
 		<div className="flex items-center justify-between">
 			<div className="flex gap-2">
 				<span className="codicon codicon-git-commit text-blue-400" />
 				<span className="font-bold">
-					{metadata.isFirst ? t("chat:checkpoint.initial") : t("chat:checkpoint.regular")}
+					{fallbackMetadata.isFirst ? t("chat:checkpoint.initial") : t("chat:checkpoint.regular")}
 				</span>
 				{isCurrent && <span className="text-muted text-sm">{t("chat:checkpoint.current")}</span>}
+				{!metadata && (
+					<span className="text-muted text-xs italic">
+						{t("chat:checkpoint.metadataUnavailable", "metadata unavailable")}
+					</span>
+				)}
 			</div>
-			<CheckpointMenu {...props} checkpoint={metadata} />
+			<CheckpointMenu {...props} checkpoint={fallbackMetadata} />
 		</div>
 	)
 }