Resources: subscriptions/listen model on modern servers (era fork) (#1630) (#1730)

Fork resource subscriptions by protocol era: legacy keeps resources/subscribe; modern (2026-07-28) models subscriptions as a filter over one long-lived subscriptions/listen stream with reconnect-by-re-listen (capped backoff), an optimistic Connecting→Listening header badge, and a fix so the browser proxy no longer blocks listen() ~60s. Closes #1630.

clients/web/src/components/elements/SubscriptionStreamBadge/SubscriptionStreamBadge.tsx

@@ -0,0 +1,27 @@
+import { Badge, Tooltip } from "@mantine/core";
+import type { ResourceSubscriptionStreamStatus } from "../../../../../../core/mcp/types.js";
+import { subscriptionStreamPresentation } from "./subscriptionStreamUtils";
+
+export interface SubscriptionStreamBadgeProps {
+  /** Lifecycle status of the modern `subscriptions/listen` stream. */
+  status: ResourceSubscriptionStreamStatus;
+}
+
+/**
+ * Status indicator for the modern-era resource-subscription listen stream
+ * (#1630). Only meaningful on the modern era — the caller gates rendering on
+ * `streamState.active`. Renders a labelled dot badge (green/yellow/gray) in the
+ * Subscriptions section header, explaining the stream in a tooltip.
+ */
+export function SubscriptionStreamBadge({
+  status,
+}: SubscriptionStreamBadgeProps) {
+  const { color, label, tooltip } = subscriptionStreamPresentation(status);
+  return (
+    <Tooltip label={tooltip} multiline w={260} withArrow>
+      <Badge variant="dot" color={color}>
+        {label}
+      </Badge>
+    </Tooltip>
+  );
+}