fix(blocks): /blocks habla prefs — modo y densidad por uix.prefs, preview sin persistencia, muere el segundo motor de densidad (P2 #5-D)

Firmado por el autor tras C («arregla también /blocks»). El shell de `/blocks`
(`web/routes/blocks/+layout@.svelte`) y el boot de cada preview
(`web/routes/blocks/_lib/BootUix.svelte`) mantenían su propio `$state` de modo
y lo pasaban a eidos por `modeSource` (muerto en f875f60b9), así que su toggle
había dejado de mover a eidos — y como el sobre `uix.prefs` es compartido con
`/uix`, la divergencia estaba a UN CLIC del toggle de docs (adversarial C, R-1).
Además implementaban la DENSIDAD a mano (`:root{--density-space-scale…}` por
`uix.dom.writeStyle`) mientras eidos ya estampa `data-density` desde prefs y la
hoja generada aplica las escalas: un segundo motor de densidad.

- Shell: `mode` y `density` DERIVADOS de las ranuras de `uix.prefs`; los toggles
  escriben `setIntent`; mueren `modeSource`, `modeListeners`, `DENSITY_SCALES` y
  el `writeStyle`; migración ÚNICA del blob `uix-blocks-prefs` al sobre de prefs
  (detalle en el cuerpo del informe / handoff).
- Preview (`BootUix`): la raíz nace con `intent` desde la URL (`mode`, `language`,
  `direction`, `density`) y `storage: false` — la preview es una PROYECCIÓN de su
  URL y ya no hidrata ni escribe el sobre compartido del documento padre
  (contaminación cruzada latente, cerrada).
- `BlockDemo`: prosa que citaba `modeSource` corregida; los ejes de la URL se leen
  de prefs.
- Ledger `check-debt.ts`: desaparecen las dos entradas de `blocks` (solo mengua).

Verificado en Chrome por el coordinador (SO oscuro sin blob ⇒ `/blocks`
coherente; toggles de modo y densidad mueven `<html data-mode/data-density>` y
el wrapper; preview `?mode=light` clara con el shell en oscuro sin tocar el sobre).
Adversarial Opus independiente (informe en el handoff). Constructor + adversarial
Opus 5; la sesión coordina.

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

scripts/check-debt.ts

@@ -37,10 +37,6 @@ export const CHECK_DEBT: Record<string, number> = {
 	// 0 → 2 (2026-09-14): retired `*Source` options — excess property + handler.
 	'web/routes/alpha/sheet/[variant]/+layout@.svelte': 2,
 	'web/routes/alpha/sheet/[variant]/+page.svelte': 1,
-	// 0 → 2 (2026-09-14): retired `*Source` options — excess property + handler.
-	'web/routes/blocks/+layout@.svelte': 2,
-	// 0 → 2 (2026-09-14): retired `*Source` options — excess property + handler.
-	'web/routes/blocks/_lib/BootUix.svelte': 2,
 	'web/routes/demos/animations/background/balastro/+page.svelte': 1,
 	'web/routes/demos/animations/background/beam/beam.svelte': 2,
 	'web/routes/demos/animations/background/bends/+page.svelte': 1,

web/routes/blocks/+layout@.svelte

@@ -13,7 +13,7 @@
 	import { onDestroy } from 'svelte';
 	import { page } from '$app/state';
 	import { createActiveUix, setActiveUix } from '$active-uix';
-	import { standardPrefsDimensions } from '$prefs';
+	import { readActivePrefsSlot, standardPrefsDimensions } from '$prefs';
 	import { Soma } from '$soma/core/soma.svelte';
 	import { siumLangs } from '$sium/langs/langs';
 	import { secsLangs } from '$libs/secs';
@@ -65,57 +65,45 @@
 	Soma.create();
 
 	// ── Axes ──────────────────────────────────────────────────────────────
-	let mode = $state<'light' | 'dark'>('light');
+	// `mode` and `density` are prefs DIMENSIONS: `uix.prefs` is the one engine
+	// that resolves them (stored intent → OS hint → default) and eidos stamps
+	// `<html data-mode>` / `<html data-density>` from those same slots, with the
+	// generated sheet rebinding the density scales per `[data-density='…']`. The
+	// shell READS the effective value — so its wrapper cannot contradict the
+	// document the way a second local state did — and WRITES intent from the
+	// topbar. Language and direction stay local for now; this batch does not
+	// move them.
 	let language = $state<Language>('es');
 	let dir = $state<'ltr' | 'rtl'>('ltr');
-	let density = $state<Density>('comfortable');
 
-	const DENSITY_SCALES: Record<Density, { space: number; control: number }> = {
-		compact: { space: 0.85, control: 0.9 },
-		comfortable: { space: 1, control: 1 },
-		spacious: { space: 1.15, control: 1.1 }
-	};
+	const activeEidos = ActiveEidos.create({ applyDom: true, theme: 'base' });
+	const modeSlot = readActivePrefsSlot<'light' | 'dark'>(uix.prefs, 'mode');
+	const densitySlot = readActivePrefsSlot<Density>(uix.prefs, 'density');
+	const mode = $derived(modeSlot?.get() ?? 'light');
+	const density = $derived(densitySlot?.get() ?? 'comfortable');
 
-	const modeListeners = new Set<(value: 'light' | 'dark') => void>();
-	const activeEidos = ActiveEidos.create({
-		applyDom: true,
-		theme: 'base',
-		modeSource: {
-			get: () => mode,
-			onChange(handler) {
-				modeListeners.add(handler);
-				return () => modeListeners.delete(handler);
-			}
-		}
-	});
-
-	// Restore once: a stored choice wins, otherwise the OS scheme decides.
+	// One-shot migration of the section's own blob: `mode` and `density` hand
+	// themselves over to the prefs envelope, which persists them from here on
+	// and follows the OS by itself when nothing is stored. The blob below stops
+	// writing the two keys, so the migration finds nothing on the next visit.
 	$effect(() => {
 		if (typeof localStorage === 'undefined') return;
 		const stored = localStorage.getItem('uix-blocks-prefs');
-		if (stored) {
-			try {
-				const blob = JSON.parse(stored);
-				if (blob.mode === 'dark' || blob.mode === 'light') mode = blob.mode;
-				if (blob.language) language = blob.language;
-				if (blob.dir) dir = blob.dir;
-				if (blob.density) density = blob.density;
-				return;
-			} catch {
-				/* ignore a corrupt blob */
-			}
+		if (!stored) return;
+		try {
+			const blob = JSON.parse(stored);
+			if (blob.language) language = blob.language;
+			if (blob.dir) dir = blob.dir;
+			if (blob.mode === 'dark' || blob.mode === 'light') uix.prefs.setIntent('mode', blob.mode);
+			if (blob.density) uix.prefs.setIntent('density', blob.density);
+		} catch {
+			/* ignore a corrupt blob */
 		}
-		mode = window.matchMedia?.('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
 	});
 
 	$effect(() => {
 		if (typeof localStorage === 'undefined') return;
-		localStorage.setItem('uix-blocks-prefs', JSON.stringify({ mode, language, dir, density }));
-	});
-
-	$effect(() => {
-		const current = mode;
-		for (const listener of modeListeners) listener(current);
+		localStorage.setItem('uix-blocks-prefs', JSON.stringify({ language, dir }));
 	});
 
 	// Language and direction are PREFS intents: they reach langs, formats and the
@@ -125,15 +113,6 @@
 		uix.prefs.setIntent('direction', dir);
 	});
 
-	// Density on :root, so portaled overlays get it too.
-	$effect(() => {
-		const d = DENSITY_SCALES[density];
-		uix.dom.writeStyle(
-			'uix-blocks-display',
-			`:root{--density-space-scale:${d.space};--density-control-scale:${d.control};}`
-		);
-	});
-
 	const currentSlug = $derived(page.url.pathname.replace(/^\/blocks\/?/, ''));
 
 	onDestroy(() => {
@@ -183,7 +162,7 @@
 					size="sm"
 					attached
 					value={[density]}
-					onValueChange={(v) => (density = (v[0] ?? density) as Density)}
+					onValueChange={(v) => uix.prefs.setIntent('density', v[0] ?? density)}
 					aria-label="Densidad"
 				>
 					<ToggleGroup.Item value="compact">−</ToggleGroup.Item>
@@ -211,7 +190,7 @@
 				size="sm"
 				variant="ghost"
 				aria-label={mode === 'light' ? 'Cambiar a modo oscuro' : 'Cambiar a modo claro'}
-				onclick={() => (mode = mode === 'light' ? 'dark' : 'light')}
+				onclick={() => uix.prefs.setIntent('mode', mode === 'light' ? 'dark' : 'light')}
 			>
 				{#if mode === 'light'}
 					<Icon.Moon size="sm" />

web/routes/blocks/_lib/BlockDemo.svelte

@@ -60,12 +60,14 @@
 	// The preview is another document with its own runtime (`BootUix` runs its
 	// own `createActiveUix`), so the section's live state does not cross the
 	// frame: the URL is the serialization the second runtime boots from. The
-	// axes are read from the FRAMEWORK's live state — the prefs dimension reads
-	// are rune-backed (per-dimension change counters) and `getThemeContext()`
-	// reads the shell's `modeSource` — so flipping a topbar toggle re-keys the
-	// iframe with the new params. The shell is the single owner of these axes
-	// (the demos' own "dir (preview only)" controls were retired with this):
-	// a demo's query string carries only its BLOCK props.
+	// axes are read from the FRAMEWORK's live state — all three are prefs
+	// dimensions and those reads are rune-backed (per-dimension change
+	// counters), `getThemeContext().mode` included, since eidos resolves the
+	// mode through the same `uix.prefs` slot the shell's toggle writes — so
+	// flipping a topbar toggle re-keys the iframe with the new params. The
+	// shell is the single owner of these axes (the demos' own "dir (preview
+	// only)" controls were retired with this): a demo's query string carries
+	// only its BLOCK props.
 	const uix = getActiveUix();
 	const eidos = ActiveEidos.require();
 	const resolvedSrc = $derived.by(() => {

web/routes/blocks/_lib/BootUix.svelte

@@ -9,7 +9,7 @@
 	 * `?mode=dark&dir=rtl&lang=en` is what the demo's iframe passes.
 	 */
 	import './reset.css';
-	import { onDestroy } from 'svelte';
+	import { onDestroy, untrack } from 'svelte';
 	import { createActiveUix, setActiveUix } from '$active-uix';
 	import { standardPrefsDimensions } from '$prefs';
 	import { Soma } from '$soma/core/soma.svelte';
@@ -37,12 +37,6 @@
 		children: Snippet;
 	} = $props();
 
-	const DENSITY_SCALES: Record<BootDensity, { space: number; control: number }> = {
-		compact: { space: 0.85, control: 0.9 },
-		comfortable: { space: 1, control: 1 },
-		spacious: { space: 1.15, control: 1.1 }
-	};
-
 	const prefsSchema = standardPrefsDimensions({
 		languages: ['es', 'en', 'fr', 'de'] as const,
 		locales: ['es-ES', 'en-US', 'en-GB', 'de-DE'] as const,
@@ -60,40 +54,34 @@
 		// still stamps `data-event-*` correctly and nothing is ever audible —
 		// which is how the section shipped from F0.
 		events: { sound: true, haptic: true, components: semaPacks },
-		prefs: { schema: prefsSchema }
+		prefs: {
+			schema: prefsSchema,
+			// The four axes enter as INTENT, so the first resolution is already the
+			// one the URL asked for — no flash, no second engine. A SNAPSHOT on
+			// purpose (`untrack`): the engine is built once and the `$effect`
+			// below owns every later move of a prop.
+			intent: untrack(() => ({ mode, language, direction: dir, density })),
+			// A preview is a PROJECTION of its URL and persists nothing. The iframe
+			// shares its origin with the section shell, so the canonical envelope is
+			// the SHELL's: with the default adapter this boot hydrated the shell's
+			// choices over the URL's and then wrote the URL's back into them.
+			storage: false
+		}
 	});
 	setActiveUix(uix);
 	Soma.create();
 
-	const modeListeners = new Set<(value: 'light' | 'dark') => void>();
-	const activeEidos = ActiveEidos.create({
-		applyDom: true,
-		theme: 'base',
-		modeSource: {
-			get: () => mode,
-			onChange(handler) {
-				modeListeners.add(handler);
-				return () => modeListeners.delete(handler);
-			}
-		}
-	});
-
-	$effect(() => {
-		const current = mode;
-		for (const listener of modeListeners) listener(current);
-	});
+	// Mode, theme, density and scaling reach `<html>` from the prefs slots eidos
+	// reads — the density scales included, rebound by the generated sheet per
+	// `[data-density='…']`.
+	const activeEidos = ActiveEidos.create({ applyDom: true, theme: 'base' });
 
+	// Re-assert the axes when a prop moves without remounting the boot.
 	$effect(() => {
+		uix.prefs.setIntent('mode', mode);
 		uix.prefs.setIntent('language', language);
 		uix.prefs.setIntent('direction', dir);
-	});
-
-	$effect(() => {
-		const d = DENSITY_SCALES[density];
-		uix.dom.writeStyle(
-			'uix-blocks-display',
-			`:root{--density-space-scale:${d.space};--density-control-scale:${d.control};}`
-		);
+		uix.prefs.setIntent('density', density);
 	});
 
 	onDestroy(() => {