Merge branch 'preserve-tree-expansion'

introduce a module-level expandedNodeIds set that tracks which
nodes the user has manually expanded. renderTree consults the set
when deciding initial visibility (falling back to the depth-based
default for a fresh load), the toggle click handler keeps the set
in sync, and both add-child save handlers add the parent's id
before triggering the re-fetch. on a fresh load the set starts
empty so root-only-open behavior is unchanged and the existing
toggle tests keep passing.

cypress/e2e/adminText.cy.js

@@ -65,6 +65,42 @@ describe('The admin text detail page', () => {
     cy.get('#text-detail li').should('contain', 'Nested Child Node')
   })
 
+  it('keeps a parent expanded after adding a child to it', () => {
+    cy.intercept('POST', '/api/nodes').as('createNode')
+    cy.intercept('GET', '/api/nodes/0').as('getNodesRefresh')
+
+    cy.get('#text-detail > ul > li > ul > li')
+      .first()
+      .find('button.toggle-children')
+      .click()
+    cy.get('#text-detail > ul > li > ul > li > ul')
+      .first()
+      .should('be.visible')
+
+    cy.get('#text-detail > ul > li > ul > li')
+      .first()
+      .children('button.add-child')
+      .click()
+    cy.get('#text-detail > ul > li > ul > li')
+      .first()
+      .children('input.child-title')
+      .type('Shemos')
+    cy.get('#text-detail > ul > li > ul > li')
+      .first()
+      .children('button.save-child')
+      .click()
+
+    cy.wait('@createNode').its('response.statusCode').should('eq', 201)
+    cy.wait('@getNodesRefresh')
+
+    cy.get('#text-detail > ul > li > ul > li > ul')
+      .first()
+      .should('be.visible')
+    cy.get('#text-detail > ul > li > ul > li > ul')
+      .first()
+      .should('contain', 'Shemos')
+  })
+
   it('newly added child persists after page reload', () => {
     cy.intercept('POST', '/api/nodes').as('createNode')
     cy.intercept('GET', '/api/nodes/0').as('getNodesRefresh')

public/js/text.js

@@ -1,3 +1,5 @@
+const expandedNodeIds = new Set();
+
 document.addEventListener('DOMContentLoaded', () => {
     const textId = window.location.pathname.split('/').pop();
 
@@ -69,7 +71,11 @@ function renderTree(nodes, textId, depth = 0) {
 
         if (node.children.length > 0) {
             const childUl = renderTree(node.children, textId, depth + 1);
-            const childrenVisible = depth === 0;
+            const childrenVisible =
+                expandedNodeIds.has(node.id) || depth === 0;
+            if (childrenVisible) {
+                expandedNodeIds.add(node.id);
+            }
             childUl.style.display = childrenVisible ? '' : 'none';
 
             const toggleBtn = document.createElement('button');
@@ -79,6 +85,11 @@ function renderTree(nodes, textId, depth = 0) {
                 const isHidden = childUl.style.display === 'none';
                 childUl.style.display = isHidden ? '' : 'none';
                 toggleBtn.textContent = isHidden ? '▼' : '▶';
+                if (isHidden) {
+                    expandedNodeIds.add(node.id);
+                } else {
+                    expandedNodeIds.delete(node.id);
+                }
             });
 
             li.appendChild(toggleBtn);
@@ -110,6 +121,7 @@ function toggleAddForm(li, parentNodeId, textId) {
         const title = input.value.trim();
         if (!title) return;
 
+        expandedNodeIds.add(parentNodeId);
         fetch('/api/nodes', {
             method: 'POST',
             headers: { 'Content-Type': 'application/json' },
@@ -155,6 +167,7 @@ function toggleBulkAddForm(li, parentNodeId, textId) {
         const count = parseInt(countInput.value);
         if (!titlePrefix || !count || count < 1) return;
 
+        expandedNodeIds.add(parentNodeId);
         fetch('/api/nodes/bulk', {
             method: 'POST',
             headers: { 'Content-Type': 'application/json' },