Update dashboard overview AI-debugging section for MCP + external agents

[Copilot]

The dashboard overview page no longer reflected the current AI debugging model: Copilot UI-in-dashboard content was removed, but the page still needed explicit agent guidance and a non-misleading screenshot path. This update keeps MCP server coverage, adds agent usage guidance, and removes dependence on outdated in-dashboard Copilot imagery.

• Dashboard overview content refresh

  • Added an ## MCP server section to clarify that dashboard telemetry is exposed to external AI agents via Aspire MCP.
  • Added a ### Using agents with the dashboard subsection with a direct link to /dashboard/ai-coding-agents/.

• Screenshot handling cleanup

  • Added a clearly marked TODO(screenshot) next to the MCP section to require a replacement image before shipping.
  • The TODO explicitly requires an external agent workflow screenshot (e.g., Copilot CLI invoking Aspire/MCP) and disallows in-dashboard Copilot chat UI imagery.

• Scope

  • Changes are limited to:
    • src/frontend/src/content/docs/dashboard/overview.mdx
  • No unrelated documentation or code paths were modified.

## MCP server

The Aspire dashboard data can be exposed to external AI coding agents through the [Aspire MCP server](/get-started/aspire-mcp-server/).

{/* TODO(screenshot): Before this docs update is shipped, add a screenshot that shows an external agent ... Do not use an in-dashboard Copilot chat UI screenshot. */}

### Using agents with the dashboard

...see [AI coding agents and the Aspire Dashboard](/dashboard/ai-coding-agents/).