feat: add download + copy file content to context menus and editor

- Add /api/pages/{id}/download and /api/pages/{id}/file-content endpoints
- Add Download + Copy content to shared context menu (_ctx_menu.html)
- Wire handlers in local-workspace and library context menus
- Add Download + Copy content to editor '...' menu for file pages
- Multi-block selection copy/cut/paste with Ctrl+C/X/V shortcuts
- Align page title with blocks start (CSS pseudo-element offset)

app/templates/library.html

@@ -718,6 +718,8 @@ function libraryPage() {
         setIcon: function (icon) { self.setItemIcon(item, icon); },
         duplicate: function (n) { self.duplicateItem(n); },
         link: function (n) { self.copyLink(n); },
+        download: function (n) { self.downloadItem(n); },
+        copyContent: function (n) { self.copyItemContent(n); },
         move: function (n) { self.openMovePicker([n.id]); },
         fav: function (n) { self.toggleFavoriteItem(n); },
         delete: function (n) { self.deleteItem(n); },
@@ -731,6 +733,34 @@ function libraryPage() {
       store.openMenu(evt, item, 'library', handlers);
     },
 
+    downloadItem(node) {
+      if (!node || node.is_folder) return;
+      var url = '/api/pages/' + node.id + '/download';
+      var a = document.createElement('a');
+      a.href = url;
+      a.style.display = 'none';
+      document.body.appendChild(a);
+      a.click();
+      document.body.removeChild(a);
+      if (window.showToast) window.showToast('Download started', 'success');
+    },
+
+    async copyItemContent(node) {
+      if (!node || node.is_folder) return;
+      try {
+        var r = await fetch('/api/pages/' + node.id + '/file-content');
+        var d = await r.json();
+        if (d.ok && d.content !== undefined) {
+          await navigator.clipboard.writeText(d.content);
+          if (window.showToast) window.showToast('Content copied to clipboard', 'success');
+        } else {
+          if (window.showToast) window.showToast('Not a text file', 'error');
+        }
+      } catch (e) {
+        if (window.showToast) window.showToast('Copy failed', 'error');
+      }
+    },
+
     // ── Drag & drop (move / reparent) ──
     onRowDragStart(evt, id) {
       if (!evt.target.closest('.drag-handle')) { evt.preventDefault(); return; }