fix(ai-sre): quote Apps en frontmatter description (unquoted colon broke Mintlify deploy) (#99)

The English description contained "...your code repositories: read code...".
An ASCII colon-space inside an unquoted YAML scalar is parsed as a mapping
separator, so Mintlify's deployment failed with "Encountered syntax error(s)"
(js-yaml: "mapping values are not allowed here"). Wrap the value in double
quotes. The zh description was unaffected (it uses a fullwidth colon).

Note: the PR-preview "Mintlify Deployment" check passed on #98, but the
stricter main deployment caught it — so validate frontmatter by YAML-parsing,
not by trusting the preview check.

Author: ysyneu

en/ai-sre/apps.mdx

@@ -1,6 +1,6 @@
 ---
 title: Apps
-description: Apps is where you manage authorized external applications in AI SRE. Each application appears as a card — currently GitHub (with room for GitLab and others later). Once authorized, AI SRE can work directly inside your code repositories: read code, investigate changes / commits / PRs, trace a PR, and (when you ask) fix a bug, open a PR, or file an issue. Its main job is to let the cloud sandbox reach your repositories safely.
+description: "Apps is where you manage authorized external applications in AI SRE. Each application appears as a card — currently GitHub (with room for GitLab and others later). Once authorized, AI SRE can work directly inside your code repositories: read code, investigate changes / commits / PRs, trace a PR, and (when you ask) fix a bug, open a PR, or file an issue. Its main job is to let the cloud sandbox reach your repositories safely."
 keywords: ["AI SRE", "Apps", "App", "GitHub", "GitHub App", "code repository", "gh", "git", "pull request", "issue", "cloud sandbox", "Customize"]
 sidebarTitle: Apps
 ---