Add ServerSettingsModal group, revert form to controlled component

Revert ServerSettingsForm to a controlled component with
expandedSections/onExpandedSectionsChange props. The form is a
dumb component — accordion state belongs to its container.

Create ServerSettingsModal group that manages:
- Accordion expand/collapse state with ListToggle expand-all button
- Add/remove/edit header pairs
- Add/remove/edit metadata pairs
- Connection mode, timeout, and OAuth changes
- All changes flow through a single onSettingsChange callback

Update ServerSettingsForm stories with useState render functions
so accordion sections are interactive.

Update UnconnectedView WithSettingsModal story to use the new
ServerSettingsModal component.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

clients/web/src/components/groups/ServerSettingsModal/ServerSettingsModal.stories.tsx

@@ -0,0 +1,62 @@
+import { useState } from "react";
+import type { InspectorServerSettings } from "@inspector/core/mcp/types.js";
+import type { Meta, StoryObj } from "@storybook/react-vite";
+import { ServerSettingsModal } from "./ServerSettingsModal";
+
+const initialSettings: InspectorServerSettings = {
+  connectionMode: "proxy",
+  headers: [
+    { key: "Authorization", value: "Bearer token-abc-123" },
+    { key: "X-Request-Id", value: "req-456" },
+  ],
+  metadata: [{ key: "userId", value: "user-789" }],
+  connectionTimeout: 30000,
+  requestTimeout: 60000,
+  oauthClientId: "my-client-id",
+  oauthClientSecret: "super-secret-value",
+  oauthScopes: "read write",
+};
+
+function InteractiveModal({
+  startSettings,
+}: {
+  startSettings: InspectorServerSettings;
+}) {
+  const [settings, setSettings] =
+    useState<InspectorServerSettings>(startSettings);
+
+  return (
+    <ServerSettingsModal
+      opened
+      settings={settings}
+      onClose={() => {}}
+      onSettingsChange={setSettings}
+    />
+  );
+}
+
+const meta: Meta<typeof ServerSettingsModal> = {
+  title: "Groups/ServerSettingsModal",
+  component: ServerSettingsModal,
+};
+
+export default meta;
+type Story = StoryObj<typeof ServerSettingsModal>;
+
+export const FullyConfigured: Story = {
+  render: () => <InteractiveModal startSettings={initialSettings} />,
+};
+
+export const EmptySettings: Story = {
+  render: () => (
+    <InteractiveModal
+      startSettings={{
+        connectionMode: "proxy",
+        headers: [],
+        metadata: [],
+        connectionTimeout: 30000,
+        requestTimeout: 60000,
+      }}
+    />
+  ),
+};