[v2] structuredContent not rendered in Tools screen — regression from v1

[ramxis]

Describe the bug
In v1 Inspector, when a tool returns both content and structuredContent
(i.e. the tool registers an outputSchema), the Tools screen displayed both:

• the content[] text/image blocks
• a dedicated collapsible JSON tree for structuredContent, which was
  extremely useful for inspecting deeply nested objects and arrays field by field

In v2, structuredContent is silently dropped from the UI. Only the
content[] blocks are rendered. There is no indication that structured output
exists, and no way to inspect it in the Tools screen.

To Reproduce
Steps to reproduce the behavior:

1. Create a simple MCP server with a tool that has an outputSchema and
   returns both content and structuredContent, e.g.:

import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { z } from "zod";

const server = new McpServer({ name: "example", version: "1.0.0" });

const ItemSchema = z.object({
  id: z.number(),
  name: z.string(),
  tags: z.array(z.string()),
});

const ResultSchema = z.object({
  items: z.array(ItemSchema),
  total: z.number(),
});

server.registerTool(
  "list_items",
  {
    title: "List Items",
    description: "Returns a list of items with structured output",
    inputSchema: {},
    outputSchema: ResultSchema.shape,
  },
  async () => {
    const result = {
      items: [
        { id: 1, name: "Item A", tags: ["foo", "bar"] },
        { id: 2, name: "Item B", tags: ["baz"] },
      ],
      total: 2,
    };
    return {
      content: [
        {
          type: "text",
          text: "Found 2 items.",
        },
      ],
      structuredContent: result,
    };
  },
);

{
  "items": [
    { "id": 1, "name": "Item A", "tags": ["foo", "bar"] },
    { "id": 2, "name": "Item B", "tags": ["baz"] }
  ],
  "total": 2
}

Expected behavior
The result panel should display both:

The content[] text block: "Found 2 items."
A dedicated "Structured Output" section rendering structuredContent
as a collapsible / inspectable JSON tree, e.g.:

Actual behavior
Only the content[] text block ("Found 2 items.") is shown in the result
panel. structuredContent is not rendered anywhere. There is no label,
section, or hint that structured output was returned at all.