Make texture and colour full kinds and drop the load-time migrations

- `Texture` and `Color` can be picked as a variable kind, a struct field
  kind and a declared port kind; a new `Texture` node hands a picture id
  into the graph. Declared, a texture is its bare id – the `$texture` tag
  stays a list-only thing.
- The `String` node is labelled "Text" like its kind; the type id stays.
- Whole-number inputs (`Item at`, `Set item`, `Sub list`, `Fill`,
  `Repeat`, `Substring`, `To text`) show no decimals (`int()` in shared.ts).
- All server projects are reseeded, so `legacyNodes.ts`,
  `migrateDeclaredLists` and the `ownerId` fallback go, with their tests.
- Note `reseed-because-of-list` moved to done/; new note `refactor-types`.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/core/graph/nodes/data/ItemAt.ts

@@ -1,14 +1,14 @@
 import { itemValue } from '../../../properties/listItems';
 import type { NodeDef } from '../../NodeRegistry';
 import { asList, asNumber } from '../../values';
-import { any, list, num } from '../shared';
+import { any, int, list } from '../shared';
 
 export const ItemAt: NodeDef = {
   type: 'ItemAt',
   label: 'Item at',
   category: 'data',
   description: 'The item at an index, counting from 0. Out of range gives 0.',
-  inputs: [list('list'), num('index')],
+  inputs: [list('list'), int('index')],
   outputs: [any('item')],
   // A color item reads as its number: the graph has no color of its own (see `portKindOf`).
   run: (_ctx, inputs) => {