feat(test-servers): mcp_app_demo preset + _meta on tool/resource defs (closes #1557)

Add an `mcp_app_demo` tool/resource preset — a self-contained MCP App widget
that exercises size-changed, ui/message, log notifications, and host-context
rendering with no external server. Requires plumbing an optional `_meta` field
through the composable test server's `ToolDefinition` and `ResourceDefinition`
so clients can read tool-level `_meta.ui.resourceUri` and resource-level
`_meta.ui.csp`.

- composable-test-server: optional `_meta` on ToolDefinition/ResourceDefinition,
  passed through to registerTool config and the resource content item.
- test-server-fixtures: `createMcpAppDemoTool()`, `createMcpAppDemoResource()`,
  inline `MCP_APP_DEMO_HTML` widget; wired into getDefaultServerConfig.
- preset-registry: `mcp_app_demo` tool + `mcp_app_demo_widget` resource presets.
- integration test asserting the `_meta` plumbing end-to-end.

Wave 1 of PR #1510 decomposition.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S3fTN8H3R8YV4yUGvZjYnX

clients/web/src/test/integration/mcp/mcp-app-demo.test.ts

@@ -0,0 +1,108 @@
+import { describe, it, expect, afterEach } from "vitest";
+import { InspectorClient } from "@inspector/core/mcp/inspectorClient.js";
+import { createTransportNode } from "@inspector/core/mcp/node/transport.js";
+import {
+  createTestServerHttp,
+  type TestServerHttp,
+  createTestServerInfo,
+  createMcpAppDemoTool,
+  createMcpAppDemoResource,
+} from "@modelcontextprotocol/inspector-test-server";
+import type { Tool } from "@modelcontextprotocol/sdk/types.js";
+
+const MCP_APP_DEMO_URI = "ui://demo/widget.html";
+
+/**
+ * Exercises the `mcp_app_demo` preset added in #1557 end-to-end: it confirms the
+ * `_meta` plumbing through the composable test server's tool/resource
+ * definitions surfaces on `tools/list` and `resources/read`, which is what the
+ * downstream Apps-host and CLI `--app-info` tests rely on.
+ */
+describe("mcp_app_demo preset", () => {
+  let client: InspectorClient | null = null;
+  let server: TestServerHttp | null = null;
+
+  afterEach(async () => {
+    if (client) {
+      try {
+        await client.disconnect();
+      } catch {
+        // Ignore disconnect errors
+      }
+      client = null;
+    }
+    if (server) {
+      try {
+        await server.stop();
+      } catch {
+        // Ignore server stop errors
+      }
+      server = null;
+    }
+  });
+
+  async function connect(): Promise<InspectorClient> {
+    server = createTestServerHttp({
+      serverInfo: createTestServerInfo("mcp-app-demo-test", "1.0.0"),
+      tools: [createMcpAppDemoTool()],
+      resources: [createMcpAppDemoResource()],
+    });
+    await server.start();
+    const connected = new InspectorClient(
+      { type: "streamable-http", url: server.url },
+      { environment: { transport: createTransportNode } },
+    );
+    await connected.connect();
+    client = connected;
+    return connected;
+  }
+
+  it("exposes tool-level _meta.ui.resourceUri on tools/list", async () => {
+    const connected = await connect();
+    const { tools } = await connected.listTools();
+    const tool = tools.find((t) => t.name === "mcp_app_demo");
+    expect(tool).toBeDefined();
+    const meta = (tool as Tool)._meta as
+      | { ui?: { resourceUri?: string; visibility?: string[] } }
+      | undefined;
+    expect(meta?.ui?.resourceUri).toBe(MCP_APP_DEMO_URI);
+    expect(meta?.ui?.visibility).toEqual(["model", "app"]);
+  });
+
+  it("exposes resource-level _meta.ui on resources/read", async () => {
+    const connected = await connect();
+    const invocation = await connected.readResource(MCP_APP_DEMO_URI);
+    const contents = invocation.result.contents;
+    expect(contents).toHaveLength(1);
+    const entry = contents[0];
+    expect(entry.mimeType).toBe("text/html");
+    expect("text" in entry ? String(entry.text) : "").toContain("mcp-app-demo");
+    const meta = entry._meta as
+      | {
+          ui?: {
+            csp?: { connectDomains?: string[]; resourceDomains?: string[] };
+            permissions?: { clipboard?: boolean };
+            prefersBorder?: boolean;
+          };
+        }
+      | undefined;
+    expect(meta?.ui?.csp).toEqual({
+      connectDomains: [],
+      resourceDomains: [],
+    });
+    expect(meta?.ui?.permissions).toEqual({ clipboard: false });
+    expect(meta?.ui?.prefersBorder).toBe(true);
+  });
+
+  it("echoes the input title from the tool handler", async () => {
+    const connected = await connect();
+    const { tools } = await connected.listTools();
+    const tool = tools.find((t) => t.name === "mcp_app_demo")!;
+    const result = await connected.callTool(tool, { title: "Widget A" });
+    expect(result.success).toBe(true);
+    const content = result.result!.content;
+    const text =
+      content[0] && "text" in content[0] ? String(content[0].text) : "";
+    expect(text).toBe('mcp_app_demo rendered with title="Widget A"');
+  });
+});