What does this PR do?

Adds code comment guidelines to AGENTS.md to prevent AI-generated comments that simply restate what the code does. This was prompted by team feedback:

Anyone else thinks we should stop allowing ai generated comments that simply restate what the function does?

Changes to AGENTS.md (kept lean, referencing the dedicated rule file):

• Do section: Added bullet linking to code comment guidelines — focus on "why", not "what"
• Don't section: Added explicit rule against restating code in comments

Changes to agents/rules/quality-code-comments.md:

• Broadened "when to comment" to include business decisions and troubleshooting context
• Added explicit guidance to skip comments entirely when no "why" is needed

No functional code changes — documentation only.

How should this be tested?

N/A — this is a documentation change to AI agent guidelines. Verify that the wording and examples align with the team's expectations for comment quality.

Human Review Checklist

• Wording in the "Do" bullet accurately captures the intent (focus on "why", skip comments when no explanation is needed)
• The link from AGENTS.md to agents/rules/quality-code-comments.md renders correctly
• Updates to the rule file ("business decisions", "troubleshooting context", skip guidance) match the team's expectations
• No unintended formatting issues in the markdown

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. N/A
• I confirm automated tests are in place that prove my fix is effective or that my feature works. N/A — docs only.

🔗 Devin session | Requested by @eunjae-lee