Add persistent per-user exclusion for duplicate Copilot instruction files

Describe the feature or problem you'd like to solve

Add persistent per-user exclusion for duplicate Copilot instruction files

Proposed solution

Summary:

GitHub Copilot CLI automatically loads supported instruction files such as  CLAUDE.md  and  AGENTS.md . When both contain duplicate or overlapping instructions, Copilot may load the same guidance twice.

The  /instructions  command can disable one file, but the change applies only to the current Copilot CLI session. There is currently no documented persistent, user-specific ignore list for excluding one repository instruction file without modifying the shared repository.

This would be useful for teams sharing repositories across multiple people and agents, including Copilot, CloudA, and Codex. A per-user configuration option to permanently exclude selected instruction files—without affecting other users or agents—would prevent duplicate instruction loading while preserving the repository structure.

Example prompts or workflows

My Claude.md file just mentions/loads Agents.md. All the instruction gets loaded twice and bloat the context..

Additional context

No response

该 issue 未指出实现文件、测试或配置入口，因此首先定位 /instructions 如何存储会话排除项，以及用户配置在哪里加载。完成标准是：按用户持久化的忽略列表能够排除选定的 repository 指令文件，同时不会更改 repository 或影响其他用户。