Enhance auto-injected copilot instructions to have more relevant instructions for scope

### Describe the feature or problem you'd like to solve

The applyTo glob pattern is not enough to scope down an instruction in large codebases with possibly hundreds of agent docs to read

### Proposed solution

Support domain/category "tags" as an addition to  applyTo  glob patterns in  .instructions.md  frontmatter, so instructions can be auto-injected based on a semantic tag assigned to files, in combination with or independently of path-based glob matching. For example, a repo currently maintaining a separate, hand-curated library of convention docs (because many conventions are cross-cutting and don't map to a clean glob) could instead express every one of those conventions as a plain  .instructions.md  file tagged by concern (e.g.  error-handling ,  security ) — removing the need for a parallel documentation system just to work around glob's path-only scoping.

### Example prompts or workflows

_No response_

### Additional context

_No response_

首先阅读 .instructions.md 的 frontmatter 处理方式以及现有的 applyTo glob 匹配行为。跟踪文件被分配 scope 的位置，以及指令被自动注入的位置；done 应包括可独立于路径匹配或与路径匹配结合工作的语义标签，并覆盖提议的错误处理和安全示例。

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