feat(classifier): Show Empty toggle; tidy the folder-tree header

- Add a "Show Empty" checkbox (classify mode) — when off, folders whose whole
  subtree contains no files are hidden, decluttering messy scans.
- Move the Show Unassigned/Assigned/Excluded/Empty filters out of the cramped
  pane header into a dedicated "Show …" toolbar row beneath it (wraps cleanly).
- Drop the "X folders selected" text from the folder-tree header (selection
  still works; updateSelectedCount guards the now-absent element).

Test: Show Empty off hides file-less folders (classify.spec.js -> 41).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

classifier/css/layout.css

@@ -76,6 +76,8 @@
 }
 
 .folder-tree-pane.collapsed .pane-header-controls,
+.folder-tree-pane.collapsed .classify-filters,
+.folder-tree-pane.collapsed .tree-filter,
 .folder-tree-pane.collapsed .folder-tree,
 .folder-tree-pane.collapsed .pane-header h3 {
     display: none;
@@ -141,13 +143,19 @@
 
 .pane-header-controls {
     display: flex;
-    flex-direction: column;
-    gap: 0.5rem;
-    align-items: flex-end;
+    flex-wrap: wrap;
+    gap: 0.3rem 0.75rem;
+    align-items: center;
+    justify-content: flex-end;
 }
 
-/* Classify-mode source-tree filters (Show Unassigned/Assigned/Excluded). */
-.classify-filters { display: inline-flex; flex-wrap: wrap; gap: 0.3rem 0.75rem; justify-content: flex-end; }
+/* Classify-mode filter row, laid out as a toolbar under the pane header. */
+.tree-toolbar {
+    display: flex; flex-wrap: wrap; align-items: center;
+    gap: 0.2rem 0.7rem; padding: 0.3rem 1rem;
+    border-bottom: 1px solid var(--border);
+}
+.tree-toolbar__label { color: var(--text-muted); font-size: 0.8rem; font-weight: 600; }
 .classify-filters .filter-count { color: var(--text-muted); font-size: 0.85em; }
 
 /* Live filter box above a file tree. */

classifier/js/app.js

@@ -147,6 +147,7 @@
             showUnassignedCheckbox: document.getElementById('showUnassignedCheckbox'),
             showAssignedCheckbox: document.getElementById('showAssignedCheckbox'),
             showExcludedCheckbox: document.getElementById('showExcludedCheckbox'),
+            showEmptyCheckbox: document.getElementById('showEmptyCheckbox'),
             exportDatasetBtn: document.getElementById('exportDatasetBtn'),
             importDatasetBtn: document.getElementById('importDatasetBtn'),
             importDatasetInput: document.getElementById('importDatasetInput'),
@@ -336,10 +337,11 @@
                     unassigned: app.dom.showUnassignedCheckbox.checked,
                     assigned: app.dom.showAssignedCheckbox.checked,
                     excluded: app.dom.showExcludedCheckbox.checked,
+                    empty: app.dom.showEmptyCheckbox.checked,
                 });
             }
         }
-        [app.dom.showUnassignedCheckbox, app.dom.showAssignedCheckbox, app.dom.showExcludedCheckbox]
+        [app.dom.showUnassignedCheckbox, app.dom.showAssignedCheckbox, app.dom.showExcludedCheckbox, app.dom.showEmptyCheckbox]
             .forEach(function (cb) { if (cb) cb.addEventListener('change', pushClassifyFilters); });
 
         // Collapse tree button

classifier/js/tree.js

@@ -42,12 +42,14 @@
     // (so unchecking Assigned+Excluded leaves only what's left to do). A folder
     // whose whole scanned subtree is filtered away is itself hidden.
     var showFilters = { unassigned: true, assigned: true, excluded: true };
+    var showEmpty = true;   // show folders that contain no files
     function setShowFilters(f) {
         showFilters = {
             unassigned: f.unassigned !== false,
             assigned: f.assigned !== false,
             excluded: f.excluded !== false,
         };
+        showEmpty = f.empty !== false;
         render();
     }
     function allFiltersOn() { return showFilters.unassigned && showFilters.assigned && showFilters.excluded; }
@@ -81,8 +83,8 @@
         for (var i = 0; i < filterTerms.length; i++) { if (t.indexOf(filterTerms[i]) === -1) return false; }
         return true;
     }
-    // Anything narrowing the tree (a name search, or a show-filter turned off).
-    function anyFilter() { return filterActive() || (classifyOn() && !allFiltersOn()); }
+    // Anything narrowing the tree (a name search, a show-filter off, or hiding empties).
+    function anyFilter() { return filterActive() || (classifyOn() && (!allFiltersOn() || !showEmpty)); }
     // One pass → the set of folder paths + file keys to render. A file shows when
     // it passes the show-filters AND (no name search, OR an ancestor folder
     // matched, OR its own path/name matches). A folder shows when it (or an
@@ -95,15 +97,22 @@
         var nf = filterActive();
         function walk(folder, ancMatched) {
             var matched = ancMatched || (nf && nameHit(folder.path || folder.name));
-            var show = false;
-            (folder.children || []).forEach(function (ch) { if (walk(ch, matched)) show = true; });
+            var show = false, hasFile = false;
+            (folder.children || []).forEach(function (ch) {
+                var r = walk(ch, matched);
+                if (r.show) show = true;
+                if (r.hasFile) hasFile = true;
+            });
             (folder.files || []).forEach(function (f) {
+                hasFile = true;
                 if (!classifyAllows(f)) return;
                 if (!nf || matched || nameHit(c.srcKeyForFile(f))) { files[c.srcKeyForFile(f)] = true; show = true; }
             });
             if (matched) show = true;
+            // "Show Empty" off → hide folders whose whole subtree holds no files.
+            if (!hasFile && !showEmpty && !matched) show = false;
             if (show) folders[folder.path] = true;
-            return show;
+            return { show: show, hasFile: hasFile };
         }
         (window.app.folderTree || []).forEach(function (root) { walk(root, false); });
         return { folders: folders, files: files };
@@ -610,9 +619,10 @@
      * Update selected folders count
      */
     function updateSelectedCount() {
+        const el = window.app.dom.selectedFoldersCount;
+        if (!el) return;   // count no longer shown in the folder-tree header
         const count = window.app.selectedFolders.size;
-        window.app.dom.selectedFoldersCount.textContent = 
-            `${count} folder${count !== 1 ? 's' : ''} selected`;
+        el.textContent = `${count} folder${count !== 1 ? 's' : ''} selected`;
     }
 
     /**

classifier/template.html

@@ -61,23 +61,27 @@
                                 <input type="checkbox" id="hideCompliantCheckbox">
                                 Hide Compliant
                             </label>
-                            <span id="classifyFilters" class="classify-filters" hidden>
-                                <label class="checkbox-label" title="Show files not yet assigned in the active tab">
-                                    <input type="checkbox" id="showUnassignedCheckbox" checked>
-                                    Show Unassigned <span class="filter-count" id="showUnassignedCount"></span>
-                                </label>
-                                <label class="checkbox-label" title="Show files already assigned in the active tab">
-                                    <input type="checkbox" id="showAssignedCheckbox" checked>
-                                    Show Assigned <span class="filter-count" id="showAssignedCount"></span>
-                                </label>
-                                <label class="checkbox-label" title="Show excluded files">
-                                    <input type="checkbox" id="showExcludedCheckbox" checked>
-                                    Show Excluded <span class="filter-count" id="showExcludedCount"></span>
-                                </label>
-                            </span>
-                            <span id="selectedFoldersCount" class="folder-count">0 folders selected</span>
                         </div>
                     </div>
+                    <div id="classifyFilters" class="classify-filters tree-toolbar" hidden>
+                        <span class="tree-toolbar__label">Show</span>
+                        <label class="checkbox-label" title="Files not yet assigned in the active tab">
+                            <input type="checkbox" id="showUnassignedCheckbox" checked>
+                            Unassigned <span class="filter-count" id="showUnassignedCount"></span>
+                        </label>
+                        <label class="checkbox-label" title="Files already assigned in the active tab">
+                            <input type="checkbox" id="showAssignedCheckbox" checked>
+                            Assigned <span class="filter-count" id="showAssignedCount"></span>
+                        </label>
+                        <label class="checkbox-label" title="Excluded files">
+                            <input type="checkbox" id="showExcludedCheckbox" checked>
+                            Excluded <span class="filter-count" id="showExcludedCount"></span>
+                        </label>
+                        <label class="checkbox-label" title="Folders that contain no files">
+                            <input type="checkbox" id="showEmptyCheckbox" checked>
+                            Empty
+                        </label>
+                    </div>
                     <input type="search" id="treeFilterInput" class="tree-filter" spellcheck="false"
                            placeholder="Filter files… (e.g. master deliverables list)" aria-label="Filter files">
                     <div id="folderTree" class="folder-tree">

tests/classify.spec.js

@@ -742,3 +742,21 @@ test('tracking-tree filter reveals matching nodes and hides the rest', async ({
     expect(names).toContain('0001');
     expect(names).not.toContain('XYZ');
 });
+
+test('Show Empty off hides folders that contain no files', async ({ page }) => {
+    await page.click('#modeClassifyBtn');
+    const r = await page.evaluate(() => {
+        window.app.folderTree = [
+            { name: 'Docs', path: 'Docs', expanded: true, scanState: 'done', children: [],
+              files: [{ originalFilename: 'a', extension: 'pdf', folderPath: 'Docs' }] },
+            { name: 'EmptyDir', path: 'EmptyDir', expanded: true, scanState: 'done', children: [], files: [] },
+        ];
+        window.app.modules.tree.render();
+        const before = Array.from(document.querySelectorAll('#folderTree .folder-item')).map((e) => e.dataset.path).sort();
+        window.app.modules.tree.setShowFilters({ unassigned: true, assigned: true, excluded: true, empty: false });
+        const after = Array.from(document.querySelectorAll('#folderTree .folder-item')).map((e) => e.dataset.path).sort();
+        return { before, after };
+    });
+    expect(r.before).toEqual(['Docs', 'EmptyDir']);   // both shown by default
+    expect(r.after).toEqual(['Docs']);                // empty folder hidden when Show Empty off
+});