Built-in research agent tells subagents to call unavailable github/get_me tool

Describe the bug

The built-in research subagent prompt tells the agent to call github/get_me first, but the GitHub MCP server exposed in the same CLI session does not provide that tool. With reasoning display enabled, the subagent visibly starts by trying to reconcile the mismatch and leaks scratchpad text like:

**Resolving function conflicts** I see that I need to call the GitHub function "get_me" first, according to the subagent instructions. However, it looks like there are only five listed GitHub functions...

This appears to be a packaged agent/tool mismatch: the built-in research-agent instructions reference an older or differently named GitHub MCP tool.

Affected version

1.0.83-3 on Linux x64.

Local evidence

Packaged agent definition:

~/.copilot/pkg/linux-x64/1.0.83-3/definitions/research.agent.yaml

Relevant prompt section:

## Critical: Work Autonomously

You work completely autonomously:
- Call `github/get_me` first to understand the user's org and identity context

The current GitHub MCP server visible to the agent exposes only these tools:

github-mcp-server-get_copilot_space
github-mcp-server-get_file_contents
github-mcp-server-list_copilot_spaces
github-mcp-server-search_code
github-mcp-server-search_users

There is no github/get_me or equivalent identity/profile tool in the available GitHub tool definitions.

Expected behavior

The built-in research-agent prompt should only instruct the subagent to call tools that are actually available in the packaged/default GitHub MCP server, or it should use the current tool namespace/name. If user identity context is unavailable, the prompt should not require a nonexistent first call.

Actual behavior

The research subagent receives an instruction to call github/get_me, cannot find the tool among the available GitHub MCP tools, and starts with visible conflict-resolution reasoning when reasoning display is enabled.

Related issues

Possibly related, but not exact:

• #4076: built-in research agent MCP/tool configurability
• #2630: subagent MCP tool availability in custom-agent / prompt contexts
• #4604: get_me with user-configured GitHub MCP auth/token injection

This issue is specifically about the packaged built-in research.agent.yaml prompt referencing github/get_me when the available built-in GitHub MCP tool list does not include it.

检查 ~/.copilot/pkg/linux-x64/1.0.83-3/definitions/research.agent.yaml，并将其中的 github/get_me 指令与列出的 GitHub MCP tools 进行比较。完成标准是：打包后的 research-agent prompt 不再要求使用不可用的 identity tool，或指定一个可用的替代工具；通过启用 reasoning display 运行 research subagent 进行验证。