fix: remove shell usage from plugin check

[aaronpowell]

Summary

• replace the shell-based symlink scan in check-plugin-structure.yml with a filesystem walk
• prevent command injection through malicious plugin directory names in pull requests
• preserve the existing workflow behavior for detecting symlinks in plugin directories

Context

This addresses the command injection reported in github/next#264 by removing the interpolated shell invocation entirely.

[Copilot]

Pull request overview

This PR updates the plugin-structure GitHub Actions workflow to eliminate shell execution when scanning plugin directories for symlinks, mitigating command-injection risk from malicious plugin names in PRs.

Changes:

• Replaces the find shell invocation with a JavaScript filesystem walk to detect symlinks.
• Keeps the existing “materialized files” checks for agents/commands/skills subdirectories intact.

Show a summary per file

File	Description
.github/workflows/check-plugin-structure.yml	Removes shell-based symlink detection and replaces it with an in-process directory traversal to avoid command injection.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 2

[Copilot]

Pull request overview

This PR hardens the check-plugin-structure GitHub Actions workflow by removing a shell-based find invocation and replacing it with a Node.js filesystem walk to detect symlinks, addressing a potential command-injection vector from untrusted plugin directory names in PRs.

Changes:

• Removed child_process.execSync usage in the workflow’s symlink detection logic.
• Added a findSymlinks() filesystem traversal using readdirSync + lstatSync to identify symlinks without invoking a shell.
• Updated symlink error reporting and added error handling for directory/entry inspection failures.

Show a summary per file

File	Description
.github/workflows/check-plugin-structure.yml	Replaces shell-based symlink scanning with a Node-based directory walk to eliminate command injection risk.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 1

[Copilot]

formattedPaths wraps user-controlled filesystem names in Markdown inline code without escaping. A crafted symlink filename containing backticks/newlines (or @mentions) can break formatting and potentially inject unwanted Markdown into the PR review body. Consider escaping Markdown special characters in filePath (at least backticks/newlines) or rendering the symlink list inside a fenced code block with safe escaping.