fix three V1.0.1 leftover tails

1. per-client links (LinkProvider.LinksForClient) now apply the
   inbound's managed Host records with the same precedence as
   subscriptions and export-all (host endpoints after fallback
   projection); zero-host inbounds keep the legacy output.
2. agent node writes no longer store the form placeholder
   address='agent', port=2053: CreateFromRequest/UpdateFromRequest
   sanitize it to the node's resolved agent address (update) or
   empty (create / unreported), port 0; normalize gains a lenient
   endpoint mode for agent writes only.
3. runtime Remote.baseURL refuses the legacy 'agent' placeholder
   with a clear no-panel-endpoint error instead of splicing it into
   a dialable https://agent:2053 URL.

internal/web/runtime/remote.go

@@ -151,11 +151,26 @@ func (r *Remote) httpClient() (*http.Client, error) {
 	return r.client, r.clientErr
 }
 
+// isAgentPlaceholderAddress reports whether addr is the placeholder the
+// node form used to store for agent nodes ("agent"). Agent nodes dial out
+// to the master and expose no panel endpoint; the write path no longer
+// stores the placeholder (see sanitizeAgentEndpoint in the node service),
+// but rows written earlier still carry it, and "agent" is a syntactically
+// valid hostname — without this guard baseURL would splice it into a
+// dialable URL (https://agent:2053/...) and do() would fire real requests
+// at whatever "agent" happens to resolve to.
+func isAgentPlaceholderAddress(addr string) bool {
+	return strings.EqualFold(addr, "agent")
+}
+
 func (r *Remote) baseURL() (string, error) {
 	addr, err := netsafe.NormalizeHost(r.node.Address)
 	if err != nil {
 		return "", err
 	}
+	if isAgentPlaceholderAddress(addr) {
+		return "", errors.New("node has no panel endpoint (agent-managed nodes cannot be dialed)")
+	}
 	scheme := r.node.Scheme
 	if scheme != "http" && scheme != "https" {
 		scheme = "https"