Document WithCommand return-value payloads (Text/Json/Markdown) for Aspire 13.3

[Copilot]

Aspire 13.3 added support for returning payload data from resource commands, including Markdown rendered in the dashboard response viewer. This PR updates the relevant docs to clearly describe the API contract, dashboard behavior, and release-note messaging.

• Custom resource commands docs

  • Renames the core section to “Returning a result from a command”.
  • Adds a focused Markdown return example using CommandResultData with CommandResultFormat.Markdown.
  • Aligns wording around ExecuteCommandResult.Data and result formats.

• Dashboard docs

  • Adds a notification-center note clarifying that Markdown command results are rendered as formatted Markdown in the text visualizer.
  • Reuses the existing response-view screenshot context to anchor the behavior.

• 13.3 changelog

  • Updates the 13.3 AppHost entry to explicitly call out structured command payloads (Text, Json, Markdown) and the CommandResults.Success(string, CommandResultData) usage pattern.

builder.AddProject<Projects.MyService>("myservice")
    .WithCommand(
        name: "migrate-database",
        displayName: "Migrate Database",
        executeCommand: _ =>
        {
            var markdown = """
                # ⚙️ Database Migration Summary
                | Table | Result |
                |---|---|
                | Customers | ✅ 1,200 rows |
                """;

            return Task.FromResult(CommandResults.Success(
                "Database migrated.",
                new CommandResultData
                {
                    Value = markdown,
                    Format = CommandResultFormat.Markdown
                }));
        });

[Copilot]

Pull request overview

This PR updates Aspire 13.3 documentation to describe the new “structured command result payloads” contract (Text/Json/Markdown), including how results flow into the dashboard notification center and how to return Markdown output from custom resource commands.

Changes:

• Updates the Aspire 13.3 “What’s new” entry to explicitly call out ExecuteCommandResult.Data payloads and Markdown-capable results.
• Renames/reshapes the custom resource commands docs section to focus on returning structured results and adds a Markdown return example.
• Clarifies dashboard behavior for Markdown command results in the text visualizer and tightens cross-link wording.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/frontend/src/content/docs/whats-new/aspire-13-3.mdx	Updates release-note wording to call out structured command payloads and the helper overload used to return them.
src/frontend/src/content/docs/fundamentals/custom-resource-commands.mdx	Renames the structured-output section and adds a Markdown return example for CommandResultData / CommandResultFormat.Markdown.
src/frontend/src/content/docs/dashboard/explore.mdx	Adds a note that Markdown results are rendered in the text visualizer and refines the link description to the commands docs.

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