Describe every value kind in one table instead of spreading it over the code

A kind like colour or texture used to be spelled out in five parallel
lists, its port type, its empty value, its glyph, its label and its list
tag - 22 literal places for texture alone. core/properties/kinds.ts now
holds one row per kind and the rest is derived from it, so adding a kind
is one row. The five literal nodes collapse into literals.ts, the six
kind menus into one helper.

Number, Text, Boolean is now the one order everywhere; the variable and
port menus used to list Boolean before Text.

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

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

@@ -0,0 +1,37 @@
+import { KIND, kindLabel, type VariableKind } from '../../../properties/kinds';
+import { coerceValue, flatDef, type PropertyDef } from '../../../properties/PropertySchema';
+import type { NodeDef } from '../../NodeRegistry';
+
+/** A node handing out one constant of a kind: its one setting, edited as that kind, is its output. */
+function literal(type: string, kind: Exclude<VariableKind, 'struct'>, description: string): NodeDef {
+  const value: PropertyDef =
+    kind === 'list'
+      ? { key: 'value', label: 'Value', kind, default: [] }
+      : kind === 'number'
+        ? { ...flatDef('value', kind, { label: 'Value' }), step: 1 }
+        : flatDef('value', kind, { label: 'Value' });
+  return {
+    type,
+    label: kindLabel(kind),
+    category: 'data',
+    description,
+    inputs: [],
+    outputs: [{ key: 'value', label: 'value', type: KIND[kind].travels }],
+    params: [value],
+    run: (_ctx, _inputs, params) => ({ outputs: { value: coerceValue(value, params.value ?? value.default) } }),
+  };
+}
+
+export const NumberLiteral = literal('Number', 'number', 'A constant number.');
+export const BooleanLiteral = literal('Boolean', 'boolean', 'A constant true/false.');
+export const StringLiteral = literal('String', 'text', 'A constant text.');
+export const TextureLiteral = literal(
+  'Texture',
+  'texture',
+  'A constant picture: a texture, one of its frames or an animation, as a sprite wears it.',
+);
+export const ListLiteral = literal(
+  'List',
+  'list',
+  'A constant list, edited item by item in the List tab – each item with its own kind.',
+);