palabras(perf): quita `provider.html` del hot path de tecleo (usa `blocks`)

Investigando el atasco de imágenes base64 se destapó un anti-patrón general:
SEIS effects del chrome (bubble/slash reposition · activate re-stamp · grip/
column-inserter/table-resize remeasure) dependían de `provider.html` como señal
de «cambió el contenido». Pero `html` es el `join('')` O(documento) de TODOS los
htmls de bloque, así que cada tecla lo recomputaba + reasignaba el string entero
(con imágenes base64 en el modelo, MB por tecla; con docs de texto grandes, O(texto)).

Migrados a `provider.blocks` / `api.blocks` — la MISMA señal (el array que el
render ya computa, referencia nueva por cambio, cubre contenido + decoraciones)
pero O(1). `html` deja de computarse en el hot path (solo en export/tests).
Comentarios en cada sitio para que no vuelva a `html`.

NOTA: este NO es el coste dominante del atasco base64 (medido: ~igual antes/
después). El residual (~4ms/MB/char) parece intrínseco del navegador — un
atributo `src` de varios MB en el DOM del contenteditable ralentiza el tecleo.
La raíz (base64 en el modelo por falta de adapter `onUploadImage`) se decide
aparte. Este commit es una mejora de hot path independiente, correcta para docs
grandes en general.

Verificado: check 0 errores palabras; Playwright — grip aparece al activar,
bubble aparece y se posiciona al seleccionar (top 363), 0 errores de consola.

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

src/uix/eidos/components/palabras/palabras-activate.svelte

@@ -219,9 +219,12 @@
 	$effect(() => {
 		const on = enabled; // re-run (and clear) when activation is turned off
 		const idPath = api.activeBlockId;
-		// Touch `html` so this effect re-runs after each re-render and
-		// re-stamps the (freshly recreated) element.
-		void api.html;
+		// Touch `blocks` (the render input — O(1) reference, new array per re-render)
+		// so this effect re-runs after each re-render and re-stamps the freshly
+		// recreated element. NOT `api.html`: that is the O(document) join of every
+		// block's HTML — reading it here recomputes it on every keystroke, which is
+		// catastrophic with large base64 image data-URLs in the model.
+		void api.blocks;
 		if (!content) return;
 		// Clear any stale marker (activation can change WITHOUT a re-render
 		// — clicking a sibling block — so the previous element keeps its

src/uix/eidos/components/palabras/palabras-column-inserter.svelte

@@ -152,9 +152,11 @@
 		inserters = out;
 	}
 
-	// Re-measure when the document changes...
+	// Re-measure when the render changes...
 	$effect(() => {
-		void api.html;
+		// `blocks` (render input, O(1) reference) not `api.html`: html is the
+		// O(document) HTML join — reading it per keystroke janks large docs / base64.
+		void api.blocks;
 		untrack(() => remeasure());
 	});
 	// ...and on scroll / resize (positions are viewport-derived).

src/uix/eidos/components/palabras/palabras-handle.svelte

@@ -135,7 +135,9 @@
 	$effect(() => {
 		const h = host();
 		const activeId = api.activeBlockId;
-		void api.html;
+		// `blocks` (render input, O(1)) not `api.html` — html is the O(document) join,
+		// janks large docs / base64 images if read per keystroke.
+		void api.blocks;
 		if (!h || !content) return;
 		let disposed = false;
 		const place = () => {

src/uix/eidos/components/palabras/palabras-table-resize.svelte

@@ -87,9 +87,11 @@
 		handles = out;
 	}
 
-	// Re-measure on document change (skip mid-drag — the live width is inline).
+	// Re-measure on render change (skip mid-drag — the live width is inline).
 	$effect(() => {
-		void api.html;
+		// `blocks` (render input, O(1)) not `api.html` — html is the O(document) join,
+		// janks large docs / base64 images if read per keystroke.
+		void api.blocks;
 		untrack(() => {
 			if (!dragKey) remeasure();
 		});

src/uix/soma/components/palabras/components/palabras-bubble-menu.svelte

@@ -41,7 +41,12 @@
 	$effect(() => {
 		state.open;
 		state.provider.selection;
-		state.provider.html;
+		// Reposition when the render changes. Depend on the `blocks` REFERENCE (O(1) —
+		// already computed for the content render, new array per change), NOT
+		// `provider.html`: `html` is the O(document) join of every block's serialized
+		// HTML, so reading it here would recompute + reallocate the whole string on
+		// every keystroke (catastrophic with large base64 image data-URLs in the model).
+		state.provider.blocks;
 		schedulePosition();
 		return () => {
 			cancelFrame?.();

src/uix/soma/components/palabras/components/palabras-slash-menu.svelte

@@ -39,7 +39,11 @@
 	$effect(() => {
 		state.open;
 		state.provider.selection;
-		state.provider.html;
+		// Reposition on render change via the `blocks` REFERENCE (O(1)), NOT
+		// `provider.html` — `html` is the O(document) join of every block's HTML, so
+		// reading it here recomputes it on every keystroke (catastrophic with large
+		// base64 image data-URLs in the model).
+		state.provider.blocks;
 		schedulePosition();
 		return () => {
 			cancelFrame?.();