fix(readme): quote Codex marketplace repo URL

[kantorcodes]

Summary:

• quote Codex marketplace Git repo URL for shell compatibility
• addresses Gemini review from PR 106 after PR auto-merged

Verification:

• README install command check passed
• marketplace JSON validates with jq
• git diff --check passed
• README guidance guard script passed

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (1 file)

• README.md - Shell quoting applied to marketplace URL on line 66; no issues detected.

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_{Reviewed by step-3.5-flash · 69,791 tokens}

[gemini-code-assist]

Code Review

This pull request updates the README.md to quote a repository URL in a shell command example. Feedback suggests using single quotes instead of double quotes to ensure the URL is treated as a literal and to avoid potential shell interpretation of special characters.