fix(tauri): restore external links in the folder picker (#225)

## Summary
- restore the GitHub and Discord links on the folder picker in the Tauri
app
- open those links through the desktop opener bridge instead of relying
on browser-only navigation behavior
- include the capability/schema updates needed for the opener path

## Testing
- npm run typecheck --workspace @codenomad/ui
- cargo check --manifest-path packages/tauri-app/src-tauri/Cargo.toml

packages/ui/src/lib/external-url.ts

@@ -0,0 +1,23 @@
+import { isTauriHost } from "./runtime-env"
+
+export async function openExternalUrl(url: string, context = "ui"): Promise<void> {
+  if (typeof window === "undefined") {
+    return
+  }
+
+  if (isTauriHost()) {
+    try {
+      const { openUrl } = await import("@tauri-apps/plugin-opener")
+      await openUrl(url)
+      return
+    } catch (error) {
+      console.warn(`[${context}] unable to open via system opener`, error)
+    }
+  }
+
+  try {
+    window.open(url, "_blank", "noopener,noreferrer")
+  } catch (error) {
+    console.warn(`[${context}] unable to open external url`, error)
+  }
+}