buildEmptyBatch: fix List/Map children → child (singular)

assembleListVector in arrow-js was crashing with
'TypeError: undefined is not an object (evaluating data.children[0].slice)'
when serializing zero-row batches whose schema included list columns.

Root cause: makeData's overloads for List and Map take `child` (singular)
— see arrow-js/src/data.ts visitList/visitMap — but we were passing
`children: [childData]` (plural array). Arrow-JS ignored the unknown
property and constructed the Data with an empty children array,
producing a List Data with no values sub-array. TypeScript didn't catch
this because the call was suffixed with `as any`, bypassing property-
shape validation entirely.

FixedSizeList was already correct (child singular). List and Map were
wrong. Passing `child: childData` for both lets IPC serialize 0-row
batches with list/map columns through httpDispatchStreamInit's token
batch path.

Also bumps echo/all_types past the list column cases on HTTP; struct/
map/union cases still surface a separate state-token issue to chase.

Author: rustyconover

src/wire/response.ts

@@ -143,19 +143,25 @@ function makeEmptyData(type: DataType): Data {
     return makeData({ type, length: 0, children, nullCount: 0 });
   }
   if (DataType.isList(type)) {
+    // Arrow-JS's makeData for List expects `child` (singular), not
+    // `children` — the latter is silently ignored (cast `as any` hides
+    // the mismatch). Without the correct key Data.children[0] is
+    // undefined, which blows up VectorAssembler when the zero-row batch
+    // is serialized into the IPC stream.
     const childData = makeEmptyData(type.children[0].type);
-    return makeData({ type, length: 0, children: [childData], nullCount: 0, valueOffsets: new Int32Array([0]) } as any);
+    return makeData({ type, length: 0, child: childData, nullCount: 0, valueOffsets: new Int32Array([0]) } as any);
   }
   if (DataType.isFixedSizeList(type)) {
     const childData = makeEmptyData(type.children[0].type);
     return makeData({ type, length: 0, child: childData, nullCount: 0 } as any);
   }
   if (DataType.isMap(type)) {
+    // Same story as List above: Map's makeData takes `child` (singular).
     const entryType = type.children[0]?.type;
     const entryData = entryType
       ? makeEmptyData(entryType)
       : makeData({ type: new Struct([]), length: 0, children: [], nullCount: 0 });
-    return makeData({ type, length: 0, children: [entryData], nullCount: 0, valueOffsets: new Int32Array([0]) } as any);
+    return makeData({ type, length: 0, child: entryData, nullCount: 0, valueOffsets: new Int32Array([0]) } as any);
   }
   return makeData({ type, length: 0, nullCount: 0 });
 }