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_

.instructions.md の frontmatter 処理と、既存の applyTo の glob マッチング動作を読むことから始めます。ファイルに scope が割り当てられる場所と、指示が自動注入される場所を追跡します。done には、パス・マッチングとは独立して、またはパス・マッチングと併用して機能するセマンティックタグを含め、提案されているエラーハンドリングとセキュリティの例をカバーする必要があります。

索引モデルが issue の本文から書いたものです。