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>

CHANGELOG.md

@@ -19,6 +19,7 @@ All notable changes to this project will be documented in this file.
 - Settings/Providers: the provider you select no longer jumps to a different one on its own. Changing the chat's model or agent, and background provider refreshes, used to move the settings selection with them.
 - Settings/Integrations: the experimental page now only lists integrations that can be installed; unavailable and Coming soon entries were removed.
 - Chat: file paths in messages now open from the session's project, even if you last browsed files in another project (thanks to @tomzx).
+- Chat: app links such as `spotify://` now ask for confirmation before opening another app. You can trust an app link type on one device and manage trusted links in Settings.
 - Files/Desktop: files opened from outside the workspace remain readable after their temporary access expires instead of failing until you reopen them (thanks to @pascalandr).
 - Diff: creating an inline comment now opens the chat and focuses the composer for your follow-up.
 - Chat: in the expanded composer, Enter now starts a new line and Cmd/Ctrl+Enter sends, so a long prompt is harder to send by accident.