chore(eidos): drop \$app/environment imports (decouple from SvelteKit)

Eidos es la capa visual y debe ser framework-agnostic. Tres componentes
metian `import { browser } from '\$app/environment'` por reflejo defensivo
SSR sin pensar la consecuencia.

relative-time.svelte:
- Drop completo del guard. El `\$effect` solo corre client-side en
  Svelte 5; el `if (!browser) return` era codigo muerto.

s-text.svelte + s-text-virtual-list.svelte:
- Aqui si hace falta guard (los `\$derived` corren durante SSR para
  inicializar valores; `getComputedStyle(el)` lanza si lo invocas en
  server). Pero reemplazo `browser` con `const isBrowser = typeof
  window !== 'undefined'` local — mismo comportamiento, cero coupling
  con SvelteKit.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/uix/eidos/components/relative-time/relative-time.svelte

@@ -15,7 +15,6 @@
 	 * Pass `updateInterval={0}` to render once and stop.
 	 */
 	import { onDestroy } from 'svelte';
-	import { browser } from '$app/environment';
 	import { getActiveUix } from '$active-uix';
 	import type {
 		RelativeTimeInput,
@@ -141,8 +140,8 @@
 
 	let timer: ReturnType<typeof setInterval> | null = null;
 
+	// `$effect` only runs client-side in Svelte 5, no SSR guard needed.
 	$effect(() => {
-		if (!browser) return;
 		if (intervalMs <= 0) return;
 		timer = setInterval(() => {
 			tick += 1;

src/uix/eidos/components/s-text-virtual-list/s-text-virtual-list.svelte

@@ -13,12 +13,15 @@
 	 * cheapest way to compute total height without mounting the rows.
 	 */
 	import './s-text-virtual-list.css';
-	import { browser } from '$app/environment';
 	import { ActiveEidos } from '$uix/eidos';
 	import { prepare, layout } from '$uix/eidos/lib/canvas-text/layout';
 	import { useContainerWidth } from '$uix/eidos/lib/canvas-text/use-canvas.svelte';
 	import type { STextVirtualListProps } from './types';
 
+	// SvelteKit-agnostic browser check — Eidos must not import from
+	// `$app/environment` (couples the visual layer to a specific framework).
+	const isBrowser = typeof window !== 'undefined';
+
 	let {
 		items = [],
 		size = 'md',
@@ -52,7 +55,7 @@
 	// Read computed style from the container — the recipe is responsible
 	// for mapping our resolved tokens to actual px / family strings.
 	const font = $derived.by(() => {
-		if (!browser || !containerEl) return '14px sans-serif';
+		if (!isBrowser || !containerEl) return '14px sans-serif';
 		const cs = getComputedStyle(containerEl);
 		const fontSize = cs.fontSize || '14px';
 		const fontFamily = cs.fontFamily || 'sans-serif';
@@ -62,7 +65,7 @@
 
 	const lineHeightPx = $derived.by(() => {
 		if (lineHeightProp != null) return lineHeightProp;
-		if (!browser || !containerEl) return 21;
+		if (!isBrowser || !containerEl) return 21;
 		const cs = getComputedStyle(containerEl);
 		const lh = cs.lineHeight;
 		if (lh && lh.endsWith('px')) return parseFloat(lh) || 21;

src/uix/eidos/components/s-text/s-text.svelte

@@ -19,7 +19,9 @@
 	 * line counts.
 	 */
 	import './s-text.css';
-	import { browser } from '$app/environment';
+	// SvelteKit-agnostic browser check — Eidos must not import from
+	// `$app/environment` (couples the visual layer to a specific framework).
+	const isBrowser = typeof window !== 'undefined';
 	import { ActiveEidos } from '$uix/eidos';
 	import { getActiveUix } from '$active-uix';
 	import { useContainerWidth, useTextLayout } from '$uix/eidos/lib/canvas-text/use-canvas.svelte';
@@ -82,7 +84,7 @@
 	// Canvas measurement is opt-in: only when `text` AND we're in the
 	// browser. SSR + `text === undefined` path stays a plain element
 	// with CSS-only clamping.
-	const canvasActive = $derived(text != null && browser);
+	const canvasActive = $derived(text != null && isBrowser);
 
 	let textEl = $state<HTMLElement | null>(null);
 	const measure = useContainerWidth(() => (canvasActive ? textEl : null));