chore(docs): commit next dev agent rules block to keep tree clean

[Zhangs-11]

The AGENTS.md agent-rules block is auto-written and re-added by next dev (see node_modules/next/dist/server/lib/generate-agent-files.js). Committing it keeps the working tree clean instead of repeatedly showing an unstaged diff.

[agegr]

Thanks, but this goes against the convention documented in the same file: AGENTS.md asks that the BEGIN:nextjs-agent-rules block be treated as generated tooling output and kept out of commits. The block's wording and presence depend on the installed next version, so committing it just moves the churn into the history (it would show up as a diff again on the next Next upgrade, and for contributors running a different version). Leaving it untracked and ignoring it in git status is the intended workflow. Closing.