ui: prefer structuredContent preview for multi-block tool results

[iqdoctor]

Why

MCP tools can return both structuredContent and content.

Per MCP spec, structuredContent is the structured machine payload, while content may include a serialized JSON mirror for backward compatibility.

Today fast-agent console rendering prefers the multi-block content[] path even when structuredContent is present. For tools like crm_tickets, that produces noisy N Text Blocks output instead of one compact structured preview.

Change

• if a tool result has structuredContent
• and content is just multiple TextContent blocks
• render one compact JSON preview from structuredContent

No MCP contract change. This is display-only.

Why this matches the standard

MCP Tools spec says servers may return structured data in structuredContent, and for backward compatibility they should also serialize it into content.

So for clients, structuredContent is the canonical structured payload; content is the compatibility mirror.

Refs:

• MCP Tools / Structured Content
• MCP schema / CallToolResult

Validation

• added a focused UI test for structured tool result rendering
• uv run scripts/lint.py
• uv run scripts/typecheck.py

[evalstate]

Hi @iqdoctor -- picking up from our chat; fast-agent was using the text content block. I've updated the handling with what I think is most appropriate; and run the prompt for the plan. let me know what you think.