fix(ui): open app deep links from chat after confirmation (#2932)

* fix(ui): open app deep links from chat after confirmation

DOMPurify's default URI policy stripped href from anchors with custom
application schemes (obsidian://, vscode://, ...), so every app link
rendered in chat was dead across web, desktop, VS Code, and mobile.

- Classify safe app-link schemes in lib/url.ts (browser-handled,
  scriptable, webview-internal, network, and self-deep-link schemes
  stay excluded) and let openExternalUrl accept them
- Keep app-link hrefs through the markdown sanitize hook
- Intercept app-link clicks in the markdown renderer and route them
  through a confirmation dialog (Trust and open / Open once, dismiss
  to cancel) mounted in the desktop/web app root and the mobile shell
- Persist per-device trusted schemes in a zustand store; trusted
  schemes open without asking again

* feat(settings): manage trusted app link schemes in General

Add an App links section to Settings > General listing the application
schemes trusted on this device with a delete action; removing a scheme
restores the confirmation dialog for it. Register the section in
settings search.

* fix(ui): enforce app link confirmation

* fix(ui): handle app links by runtime

* fix(vscode): keep app links unsupported

* fix(settings): clarify trusted app links

---------

Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/components/chat/message/parts/DOCUMENTATION.md

@@ -54,7 +54,8 @@ Use this doc when you ask an agent to change tool/header/description behavior.
 - Assistant markdown treats raw HTML as inert visible text. The final generated
   HTML is sanitized as defense in depth, with script and style elements
   forbidden, so message content cannot inject active DOM or application-wide
-  CSS into any runtime surface.
+  CSS into any runtime surface. Safe custom application links go through the
+  app-link confirmation flow in every supported renderer, including VS Code.
 - Final assistant Markdown rendering is independent from image gallery
   extraction: gallery presence never changes the chat body. Assistant image
   syntax consistently renders as a shared image icon followed by its filename,