Add agent-sh/agnix to clean code linters collection

agnix is a linter and LSP for AI agent configurations (CLAUDE.md,
AGENTS.md, SKILL.md, hooks, MCP). 342 rules, autofixes, SARIF output,
and plugins for VS Code, Neovim, JetBrains, and Zed.

Author: avifenesh

collections/clean-code-linters/index.md

@@ -39,6 +39,7 @@ items:
  - nicklockwood/SwiftFormat
  - super-linter/super-linter
  - stylelint/stylelint
+ - agent-sh/agnix
 display_name: Clean code linters
 created_by: holman
 ---