fix(docs): drop sidebar entry for a page that was never added

sidebars.js referenced ui-testing-with-kane-cli, but docs/ui-testing-with-kane-cli.md
exists on neither stage nor main. Docusaurus validates sidebar ids at load, so
"npx docusaurus build" fails on stage today:

  Invalid sidebar file at "sidebars-unified.js".
  These sidebar document ids do not exist:
  - ui-testing-with-kane-cli

This is pre-existing and unrelated to the mobile docs, but it blocks the build
check on any docs PR, so it is fixed here in its own commit. If the page is
being written, replace this commit by adding the file instead.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: 2 people

sidebars.js

@@ -5246,11 +5246,6 @@ module.exports = {
             label: "API Testing",
             id: "api-testing-with-kane-cli",
           },
-          {
-            type: "doc",
-            label: "UI Testing",
-            id: "ui-testing-with-kane-cli",
-          },
           {
             type: "doc",
             label: "AI Coding Agents",