Let a variable hold a list

A variable could only be a number, a text or a yes/no, so every set of values had
to be smuggled through a string - which is where Tetris got its unreadable
"03066326048763714" colours from. A list is now a value of its own, with an item
kind (number, text, yes/no, colour) that decides how the inspector reads the one
comma-separated line it is typed as, and eight nodes to work with: List, Fill,
Count, Item at, Set item, Sub list, Join lists, Index of.

Two traps came with it. An array is typeof 'object', so every place that told a
value from an entity had to learn the difference, or a list would have been
passed around as a game object. And a value was compared by identity in three
places - with lists that marks everything as an overridden property after each
reload, so those comparisons now compare contents.

There is no list of objects: a list is written to the project file and an object
is a live handle that no reload survives. A set of objects stays a list of names.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/core/graph/nodes/index.ts

@@ -55,6 +55,14 @@ import { Subtract } from './data/Subtract';
 import { Time } from './data/Time';
 import { ToNumber } from './data/ToNumber';
 import { ToText } from './data/ToText';
+import { Concat } from './data/Concat';
+import { Count } from './data/Count';
+import { Fill } from './data/Fill';
+import { IndexOf } from './data/IndexOf';
+import { ItemAt } from './data/ItemAt';
+import { ListLiteral } from './data/ListLiteral';
+import { SetItem } from './data/SetItem';
+import { SubList } from './data/SubList';
 import { OnClick } from './events/OnClick';
 import { OnCollisionEnter } from './events/OnCollisionEnter';
 import { OnCollisionExit } from './events/OnCollisionExit';
@@ -140,6 +148,15 @@ export const BUILT_IN_NODES: readonly NodeDef[] = [
   And,
   Or,
   Not,
+  // data: lists
+  ListLiteral,
+  Fill,
+  Count,
+  ItemAt,
+  SetItem,
+  SubList,
+  Concat,
+  IndexOf,
   // data: vectors and input
   Length,
   Distance,