sema: VisualChannel preserves structural data-intent on cleanup

The channel writes `data-intent` from `signal.intent` during the hold,
but `data-intent` is also the structural attr the morfo of components
like Toast.Item writes from `v.propRef('intent')`. Removing it on
cleanup erased the structural value — the toast lost its tinting after
the announce signal expired.

Fix: save the prior `data-intent` value before overwrite, restore it on
cleanup. General principle — a channel should clean only what it wrote.
Other signal attrs (`data-event*`, `data-event-family`) are signal-
specific so no collision.

Tests: structural data-intent survives the hold; mismatched signal vs
structural intent (edge case) restores the structural value.

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

src/uix/sema/chans/visual.test.ts

@@ -165,4 +165,51 @@ describe('VisualChannel', () => {
 		const channel = new VisualChannel()
 		expect(channel.id).toBe('visual')
 	})
+
+	it('preserves a structural data-intent that existed before the signal', async () => {
+		// Toast.Item carries a structural data-intent from morfo (v.propRef('intent')).
+		// The channel must not erase it during cleanup.
+		target.setAttribute('data-intent', 'risk')
+
+		const channel = new VisualChannel()
+		const promise = channel.handle({
+			target,
+			name: 'announce',
+			family: 'alert',
+			intent: 'risk',
+			id: 'sig-1',
+			hold: 100
+		})
+
+		expect(target.getAttribute('data-intent')).toBe('risk')
+
+		vi.advanceTimersByTime(100)
+		await promise
+
+		// signal attrs gone, structural data-intent restored
+		expect(target.hasAttribute('data-event')).toBe(false)
+		expect(target.getAttribute('data-intent')).toBe('risk')
+	})
+
+	it('restores a different prior data-intent when signal carries another value', async () => {
+		// Edge case: structural intent and signal intent disagree (would be unusual
+		// but the channel should still leave the structural value intact).
+		target.setAttribute('data-intent', 'neutral')
+
+		const channel = new VisualChannel()
+		const promise = channel.handle({
+			target,
+			name: 'announce',
+			intent: 'threat',
+			id: 'sig-2',
+			hold: 100
+		})
+
+		expect(target.getAttribute('data-intent')).toBe('threat')
+
+		vi.advanceTimersByTime(100)
+		await promise
+
+		expect(target.getAttribute('data-intent')).toBe('neutral')
+	})
 })

src/uix/sema/chans/visual.ts

@@ -17,6 +17,11 @@ import type { Channel } from './types'
  * Los dos opcionales son proyección al DOM de la metadata semántica que
  * Eidos consume (`[data-intent="risk"]`, `[data-event-family="alert"]`).
  *
+ * `data-intent` es el único nombre que puede coincidir con un attr
+ * estructural ya escrito por el morfo del componente. El canal lo guarda
+ * antes de overwrite y lo restaura al limpiar (save/restore) — regla
+ * general: un canal solo debe limpiar lo que escribió.
+ *
  * Es un detalle de este canal, no API pública del engine: si en el futuro
  * otros canales (sound, vibra) quieren cosas distintas en sus respectivos
  * planos, las definirán por separado.
@@ -69,7 +74,13 @@ export class VisualChannel implements Channel {
 
 		const id = signal.id ?? ''
 
-		// Escribir atributos
+		// `data-intent` puede coincidir con un attr estructural ya escrito por
+		// el morfo del componente (p. ej. Toast.Item lleva `data-intent` desde
+		// `v.propRef('intent')`). Guardamos el valor previo y lo restauramos en
+		// cleanup para no borrar el attr estructural — el canal debe limpiar
+		// solo lo que escribió.
+		const priorIntent = signal.intent ? target.getAttribute('data-intent') : null
+
 		target.setAttribute('data-event', signal.name)
 		target.setAttribute('data-event-id', id)
 		target.setAttribute('data-event-phase', 'active')
@@ -89,7 +100,10 @@ export class VisualChannel implements Channel {
 		target.removeAttribute('data-event-id')
 		target.removeAttribute('data-event-phase')
 		if (signal.family) target.removeAttribute('data-event-family')
-		if (signal.intent) target.removeAttribute('data-intent')
+		if (signal.intent) {
+			if (priorIntent !== null) target.setAttribute('data-intent', priorIntent)
+			else target.removeAttribute('data-intent')
+		}
 	}
 
 	private resolveHoldMs(signal: SemanticSignal): number {