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/groups/ProtocolEntry/ProtocolEntry.stories.tsx

@@ -176,7 +176,7 @@ const subscriptionNotificationEntry: MessageEntry = {
     jsonrpc: "2.0",
     method: "notifications/resources/list_changed",
     params: {
-      _meta: { "io.modelcontextprotocol/subscriptionId": "sub-abc123" },
+      _meta: { "io.modelcontextprotocol/subscriptionId": "listen:0" },
     },
   },
 };
@@ -231,7 +231,8 @@ export const ModernInputRequired: Story = {
   },
 };
 
-// Modern-era: a `server/discover` probe, flagged with the "modern" frame badge.
+// Modern-era: a `server/discover` probe (a modern-only method). The connection
+// era is shown once in the panel header, not per entry.
 export const ModernDiscoverFrame: Story = {
   args: {
     entry: discoverEntry,
@@ -249,6 +250,25 @@ export const ModernSubscriptionNotification: Story = {
   },
 };
 
+// Embedded (monitoring-sidebar) layout of a subscription notification: the
+// `sub … listen-id` tag rides the top line (beside the direction) so the method
+// badge on the line below gets the full narrow-column width (#1630).
+export const EmbeddedSubscriptionNotification: Story = {
+  args: {
+    entry: subscriptionNotificationEntry,
+    isPinned: false,
+    isListExpanded: false,
+    embedded: true,
+  },
+  decorators: [
+    (Story) => (
+      <Box w={340}>
+        <Story />
+      </Box>
+    ),
+  ],
+};
+
 // Embedded (monitoring-sidebar) layout with a long resource URI: the target sits
 // in a horizontal scroll area rather than truncating with an ellipsis. Wrapped
 // in the pinned column's width so the overflow is visible.