structure_test: limit regex checks to small non-binary files

[imjasonh]

This fails faster when regex tests are requested on large (>1 MB) or binary files (containing null bytes)

[Copilot]

Pull Request Overview

This pull request adds validation to limit regex checks in file structure tests to small, non-binary files. The change prevents regex matching on files larger than 1MB or containing binary data (null bytes), causing faster failure for inappropriate file types.

Key changes:

• Added size limit validation (1MB maximum) for files before regex matching
• Added binary file detection by checking for null bytes in the first 8KB
• Created comprehensive test coverage for both size and binary content validation scenarios

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
pkg/structure/structure.go	Added size and binary validation logic with 1MB limit constant
pkg/structure/structure_test.go	Added comprehensive test cases covering size limits and binary detection

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}