get_copilot_space tool does not return attached file contents from Copilot Spaces

## Description

The `get_copilot_space` tool only returns the space's metadata (name, description, and general_instructions), but does **not** return the contents of files that have been explicitly attached to the space as knowledge sources.

## Steps to Reproduce

1. Create a Copilot Space (e.g., within a GitHub organization).
2. Attach one or more files as knowledge sources to the space (e.g., `.md`, `.sql`, `.java` files).
3. Write `general_instructions` that reference those files (e.g., "always read `myFile.md` first...").
4. Use the `get_copilot_space` MCP tool (via VS Code GitHub Copilot agent) to retrieve the space.

## Expected Behavior

The tool should return the contents of the attached knowledge source files so that the agent can actually read and use them when answering questions, as directed by the `general_instructions`.

## Actual Behavior

The tool returns only 3 resources:
- `name`
- `description`
- `general_instructions`

The attached files are completely absent from the tool response, even when they are confirmed to be present and attached in the Copilot Space UI.

## Impact

This makes the `get_copilot_space` tool effectively unable to fulfill its intended purpose as a subject matter expert knowledge base. The `general_instructions` can instruct the agent to read specific files, but the agent has no way to access them through the tool.

## Environment

- Tool: `get_copilot_space` (GitHub MCP Server)
- Client: VS Code GitHub Copilot agent (Copilot Chat)
- Space owner: GitHub Organization (private)
- Date: 2026-02-26

## Suggested Fix

The tool response should include the contents (or at minimum the URIs/download URLs) of files attached to the Copilot Space as knowledge sources, so the agent can read them during the session.