feat: keyboard shortcuts — backtick, number keys, arrow navigation in handleGlobalKeydown

- Backtick (Backquote) toggles view dropdown in grid mode only (not fullscreen)
- Number keys 1-9 directly switch views (1=all, 9=hidden, 2-8=user views)
- Arrow keys navigate within open dropdown using [role="menuitem"] elements
- Enter activates the focused dropdown item
- Escape closes open dropdown when one is visible
- Shortcuts disabled when typing in INPUT/TEXTAREA/SELECT
- Input guard applied globally (not just for comma shortcut)

Tests added:
- test_handle_global_keydown_has_backtick_handler
- test_handle_global_keydown_has_number_key_shortcuts
- test_backtick_only_on_grid_not_fullscreen

All 229 tests pass (226 existing + 3 new)

muxplex/frontend/app.js

@@ -1953,25 +1953,82 @@ function switchSettingsTab(tabName) {
 
 /**
  * Global keydown handler.
- * If settings are open: Escape closes settings.
- * Comma key (not in inputs) opens settings.
- * In fullscreen: Escape returns to grid.
+ * Settings open: Escape closes settings, return.
+ * Ignore shortcuts when typing in INPUT/TEXTAREA/SELECT.
+ * Comma key (not in inputs, no ctrl/meta) opens settings.
+ * Grid overview only: backtick toggles dropdown, number keys 1-9 switch views.
+ * Arrow keys + Enter navigate within open dropdown.
+ * Escape closes open dropdown.
+ * Fullscreen: Escape calls closeSession().
  * @param {KeyboardEvent} e
  */
 function handleGlobalKeydown(e) {
+  // Settings open: only Escape closes it, then bail
   if (_settingsOpen) {
-    if (e.key === 'Escape') {
-      closeSettings();
-    }
+    if (e.key === 'Escape') { closeSettings(); }
     return;
   }
-  if (e.key === ',' && !e.ctrlKey && !e.metaKey) {
+  // Determine if focus is inside a text input
   const tag = document.activeElement && document.activeElement.tagName;
-    if (tag !== 'INPUT' && tag !== 'TEXTAREA' && tag !== 'SELECT') {
+  const inInput = (tag === 'INPUT' || tag === 'TEXTAREA' || tag === 'SELECT');
+  // Comma key (not in inputs, no ctrl/meta) opens settings
+  if (e.key === ',' && !e.ctrlKey && !e.metaKey && !inInput) {
     openSettings();
     return;
   }
+  // View dropdown shortcuts — grid overview only, not in input, no ctrl/meta
+  if (_viewMode === 'grid' && !inInput && !e.ctrlKey && !e.metaKey) {
+    // Backtick toggles the view dropdown
+    if (e.code === 'Backquote') {
+      e.preventDefault();
+      toggleViewDropdown();
+      return;
     }
+    // Number keys 1-9: 1=all, 9=hidden, 2-8=user views by index (num-2)
+    if (e.code && e.code.startsWith('Digit')) {
+      const num = parseInt(e.key, 10);
+      if (num >= 1 && num <= 9) {
+        const views = (_serverSettings && _serverSettings.views) || [];
+        if (num === 1) {
+          switchView('all');
+        } else if (num === 9) {
+          switchView('hidden');
+        } else {
+          const vIdx = num - 2;
+          if (vIdx < views.length) { switchView(views[vIdx].name); }
+        }
+        return;
+      }
+    }
+  }
+  // Arrow key navigation within open dropdown
+  const menu = $('view-dropdown-menu');
+  if (menu && !menu.classList.contains('hidden')) {
+    if (e.key === 'ArrowDown' || e.key === 'ArrowUp') {
+      e.preventDefault();
+      const items = Array.from(menu.querySelectorAll('[role="menuitem"]'));
+      if (items.length > 0) {
+        const focusedEl = document.activeElement;
+        let itemIdx = items.indexOf(focusedEl);
+        if (e.key === 'ArrowDown') {
+          itemIdx = (itemIdx + 1) % items.length;
+        } else {
+          itemIdx = (itemIdx - 1 + items.length) % items.length;
+        }
+        items[itemIdx].focus();
+      }
+      return;
+    }
+    if (e.key === 'Enter') {
+      const focusedEl = document.activeElement;
+      if (menu.contains(focusedEl)) { focusedEl.click(); return; }
+    }
+    if (e.key === 'Escape') {
+      closeViewDropdown();
+      return;
+    }
+  }
+  // Fullscreen: Escape calls closeSession
   if (_viewMode === 'fullscreen' && e.key === 'Escape') {
     e.preventDefault();
     closeSession();

muxplex/tests/test_frontend_js.py

@@ -3165,3 +3165,67 @@ def test_switch_view_patches_state() -> None:
     body = match.group(1)
     assert "PATCH" in body, "switchView must use PATCH method"
     assert "/api/state" in body, "switchView must PATCH /api/state"
+
+
+# ---------------------------------------------------------------------------
+# Keyboard Shortcuts — Backtick, Number Keys, Arrow Navigation (task-7)
+# ---------------------------------------------------------------------------
+
+
+def test_handle_global_keydown_has_backtick_handler() -> None:
+    """handleGlobalKeydown must handle backtick/Backquote key to toggle view dropdown."""
+    match = re.search(
+        r"function handleGlobalKeydown\s*\(e\)\s*\{(.*?)\n\}",
+        _JS,
+        re.DOTALL,
+    )
+    assert match, "handleGlobalKeydown function not found"
+    body = match.group(1)
+    has_backtick = (
+        "Backquote" in body
+        or "e.key === '`'" in body
+        or 'e.key === "`"' in body
+    )
+    assert has_backtick, (
+        "handleGlobalKeydown must handle backtick/Backquote key to toggle view dropdown"
+    )
+    assert "toggleViewDropdown" in body, (
+        "handleGlobalKeydown backtick handler must call toggleViewDropdown"
+    )
+
+
+def test_handle_global_keydown_has_number_key_shortcuts() -> None:
+    """handleGlobalKeydown must call switchView for number keys 1–9."""
+    match = re.search(
+        r"function handleGlobalKeydown\s*\(e\)\s*\{(.*?)\n\}",
+        _JS,
+        re.DOTALL,
+    )
+    assert match, "handleGlobalKeydown function not found"
+    body = match.group(1)
+    assert "switchView" in body, (
+        "handleGlobalKeydown must call switchView for number keys 1–9"
+    )
+    has_number_handling = (
+        "Digit" in body or "parseInt" in body
+    )
+    assert has_number_handling, (
+        "handleGlobalKeydown must handle number key codes (e.g. e.code.startsWith('Digit'))"
+    )
+
+
+def test_backtick_only_on_grid_not_fullscreen() -> None:
+    """Backtick handler must check _viewMode === 'grid' (not active in fullscreen)."""
+    match = re.search(
+        r"function handleGlobalKeydown\s*\(e\)\s*\{(.*?)\n\}",
+        _JS,
+        re.DOTALL,
+    )
+    assert match, "handleGlobalKeydown function not found"
+    body = match.group(1)
+    assert "_viewMode" in body, (
+        "handleGlobalKeydown backtick handler must check _viewMode"
+    )
+    assert "'grid'" in body, (
+        "handleGlobalKeydown must check _viewMode === 'grid' before handling backtick/number shortcuts"
+    )