Let a list hold structs, and read or write variables in bundles

A list item may now be a struct. The depth is bounded in the declaration
rather than by a comment: FieldKind (number|text|boolean|color) says what a
struct field holds, ListItemKind adds struct on top and says what a list
holds, so list -> struct -> primitive is the deepest storable shape and
sameValue stays finite. A struct item renders inline in the List tab, which
is why it needs no path in the slot address.

Four paths silently assumed a list item was a primitive: sameValue compared
items with ===, textOf would have printed [object Object], asListItem turned
a struct into text on Set item and Fill, and Index of used indexOf, which is
reference equality and could never have found a struct.

Tetris now runs on bundles. shapes is 112 {x, y} structs instead of 224 loose
numbers, piece and the candidate are structs, so Next move hands back a whole
candidate and each strand packs only the field it changes, since mergeStruct
leaves the rest standing. Declared behavior ports drop 49 -> 35, the master's
variables 18 -> 13, its graph 84/94 -> 69/76 nodes/edges.

Get variables and Set variables declare their ports from a list of variable
names, the way Pack and Expand already do, so one node can read or write
several at once. Renaming a variable rewires them, because there the port key
is the variable name.

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

src/core/commands/variableCommands.ts

@@ -18,6 +18,7 @@ import {
 } from '../properties/PropertySchema';
 import { type Removed, removeFirst, restoreAt } from '../util/list';
 import { type Command, CommandError } from './Command';
+import { renameVariablePorts } from './portCommands';
 import { requireBehavior } from './require';
 
 /** The variable's default value is written to `props` as well. */
@@ -133,6 +134,7 @@ export class RenameVariableCommand implements Command {
     }
     // Every node that picks a variable stores it under the param key `variable`.
     for (const node of asset.graph.nodes) if (node.params.variable === from) node.params.variable = to;
+    renameVariablePorts(asset.graph, from, to);
   }
 }