Add /ui exception for mini-toc generation (flutter#9164)

This allows index pages linked to from the breadcrumbs to be generated
properly, such as the text index page. They were empty since the
generation didn't account for `/ui` having multiple entries in the
sidenav.

src/_layouts/toc.html

@@ -1,6 +1,7 @@
 ---
 layout: default
 toc: false
+sitemap: false
 ---
 
 {% assign url = page.url | regex_replace: '/index$|/index.html$|/$' -%}
@@ -17,7 +18,7 @@
   {% else -%}
     {% assign path = path | append: '/' | append: path_part -%}
   {% endif -%}
-  {% if forloop.index0 > 0 -%}
+  {% if forloop.index0 > 0 and path != '/ui' -%}
     {% assign topics = topics | where: "permalink", path -%}
     {% assign topics = topics[0].children | where_exp:"item", "item != 'divider'" -%}
   {% endif -%}

src/ui/design/index.md

@@ -1,6 +1,6 @@
 ---
 layout: toc
-title: Design
+title: Design & theming
 description: Content covering designing Flutter apps.
 sitemap: false
 ---

src/ui/index.md

@@ -1,5 +1,4 @@
 ---
-layout: toc
 title: Building user interfaces with Flutter
 short-title: UI
 description: Introduction to user interface development in Flutter.

src/ui/interactivity/gestures/index.md

@@ -1,5 +1,6 @@
 ---
 title: Taps, drags, and other gestures
+short-title: Gestures
 description: How gestures, such as taps and drags, work in Flutter.
 ---