Prefer named dev-server URLs over raw localhost ports

[jakeleventhal]

The sidebar and browser show the underlying localhost listener for a dev server, even when Portless, ngrok, or Tailscale Serve already has a stable name for that same process. Those ports change; the named URL does not.

Discover Portless routes, active ngrok HTTP tunnels, and Tailscale Serve status, and offer the named URL as the shortcut. Proposed priority for the current worktree: ngrok, then Tailscale Serve, then Portless, then localhost. Remote environments should open ngrok and Tailscale URLs directly; remote Portless can fall back to the listener.

#6514 implements this and was closed pending agreement on that discovery scope and shortcut priority.