fix(eidos): QrCode size tokens use literal var names (recipe contract)

Size was applied via `var(--qr-code-size-${resolvedSize})` (interpolated), so
the literal token names never appeared in source and the recipe-css-contract
test flagged --qr-code-size-{xs..xl} as orphaned. Use an explicit literal map so
each name appears verbatim; behaviour unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/uix/eidos/components/qr-code/qr-code.svelte

@@ -28,8 +28,17 @@
 
 	const eidos = ActiveEidos.require();
 	const resolvedSize = $derived(eidos.resolve(size, 'md'));
+	// Literal map (not interpolated) so each --qr-code-size-* token name appears
+	// verbatim in the source — the recipe contract scans for exact token names.
+	const SIZE_VARS = {
+		xs: 'var(--qr-code-size-xs)',
+		sm: 'var(--qr-code-size-sm)',
+		md: 'var(--qr-code-size-md)',
+		lg: 'var(--qr-code-size-lg)',
+		xl: 'var(--qr-code-size-xl)'
+	} as const;
 	const px = $derived(
-		typeof resolvedSize === 'number' ? `${resolvedSize}px` : `var(--qr-code-size-${resolvedSize})`
+		typeof resolvedSize === 'number' ? `${resolvedSize}px` : SIZE_VARS[resolvedSize]
 	);
 
 	// A logo needs max redundancy + a cleared centre to stay scannable.