fix(tree-view): target branches for emerge-expand/collapse

Morfo declaraba target='item' para emerge-expand y emerge-collapse,
pero los items son hojas — no se expanden. El stamp del data-event-*
debe aterrizar en el branch (data-tree-view-branch), que es el part
que realmente revela/oculta contenido.

- Morfo: target: v.partRef('item') → v.partRef('branch') en ambos
  events de emerge. commit-select sigue en item (selección aplica
  tanto a leaves como a branches).
- Pack: selector `onItem(emerge-*)` → `onBranch(emerge-*)`. Las dos
  cascadas de emerge ahora matchean el elemento correcto en DOM.

tree-grid no afectado: su Row es a la vez item y branch (data-has-
children + data-expanded en el mismo part), así que target='row'
ya estaba correcto.

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

src/uix/morfo/components/tree-view.ts

@@ -32,22 +32,28 @@ export const treeViewMorfo = {
 			// sección desplegable)." Tree expand fits exactly. Was
 			// misclassified as `shift.navigate` (which is for context/regime
 			// change, not content revealing).
+			//
+			// Target is `branch` (not `item`): items are leaves — they
+			// don't expand. The data-event-* stamp lands on the branch
+			// element (`data-tree-view-branch`), which is what the sema
+			// pack selector targets.
 			name: 'emerge-expand',
 			semantic: {
 				family: 'emerge',
 				verb: 'expand',
-				target: v.partRef('item'),
+				target: v.partRef('branch'),
 				sequence: 'post'
 			}
 		},
 		{
 			// Collapse a node — per book cap. 26: "emerge.collapse — una
-			// región se contrae."
+			// región se contrae." Target is `branch` for the same reason
+			// as emerge-expand above.
 			name: 'emerge-collapse',
 			semantic: {
 				family: 'emerge',
 				verb: 'collapse',
-				target: v.partRef('item'),
+				target: v.partRef('branch'),
 				sequence: 'post'
 			}
 		}

src/uix/sema/components/tree-view.ts

@@ -6,10 +6,12 @@ import type { Sema } from '../sema-map';
 /**
  * TreeView perceptual defaults — SOFT EMERGE + COMMIT.
  *
- * TreeView has three event surfaces, all targeting the `item` part:
- *   - `commit-select` (commit.select, affirm) — leaf or branch selected
- *   - `emerge-expand` (emerge.expand) — branch reveals children
- *   - `emerge-collapse` (emerge.collapse) — branch hides children
+ * TreeView has three event surfaces:
+ *   - `commit-select` on `item` — leaf or branch selected (affirm intent
+ *      via family deltas). Item part covers both leaves and branches
+ *      from the selection standpoint.
+ *   - `emerge-expand` on `branch` — branch reveals children.
+ *   - `emerge-collapse` on `branch` — branch hides children.
  *
  * Strategy (book cap. 22 §10 + cap. 26 emerge open/close discipline):
  *   - EXPAND: `emerge.soft` (gain 0.08) — content reveals, ascending
@@ -21,15 +23,14 @@ import type { Sema } from '../sema-map';
  *     content surfaces elsewhere), and the select chime mustn't
  *     compete with that downstream signal.
  *
- * Note on target: morfo declares all three events targeting `item`
- * (leaves). Branches also have role="treeitem" but a different part
- * marker (`data-tree-view-branch`). If branches end up emitting at
- * runtime without the `data-tree-view-item` marker, this cascade will
- * miss them — a known concern noted in the morfo declaration audit.
- * The pack follows the morfo declaration verbatim; any mismatch is a
- * morfo-level fix outside this pack's scope.
+ * Target split: expand/collapse target `branch` because items are
+ * leaves — they don't expand. The DOM marker on a branch is
+ * `data-tree-view-branch`, distinct from `data-tree-view-item`. The
+ * selectors below honour that split.
  */
 
+const onBranch = (matchers?: Parameters<typeof semaSelector<typeof treeViewMorfo>>[2]) =>
+	semaSelector(treeViewMorfo, 'branch', matchers);
 const onItem = (matchers?: Parameters<typeof semaSelector<typeof treeViewMorfo>>[2]) =>
 	semaSelector(treeViewMorfo, 'item', matchers);
 
@@ -37,11 +38,11 @@ export const treeViewSema: Sema = {
 	name: 'tree-view',
 	cascade: [
 		{
-			selector: onItem({ eventName: 'emerge-expand' }),
+			selector: onBranch({ eventName: 'emerge-expand' }),
 			sound: soundTuning('emerge.soft')
 		},
 		{
-			selector: onItem({ eventName: 'emerge-collapse' }),
+			selector: onBranch({ eventName: 'emerge-collapse' }),
 			sound: soundTuning('emerge.exit.soft')
 		},
 		{