Clarify signed commit guidance for mcore-engineers (#7597)

Signed-off-by: Jingyue Wu <jingyuew@nvidia.com>

Author: wujingyue

AGENTS.md

@@ -24,12 +24,14 @@ skill keyword — infer it from the artifact you read.
 
 - All PRs must be created as **drafts**. Use `gh pr create --draft` or the GitHub UI draft option.
 - Never push branches directly to `https://github.com/NVIDIA/Megatron-LM`. You must push your branch to a personal fork (e.g. `https://github.com/<your-username>/Megatron-LM`), then open a PR from the fork's branch against `NVIDIA/Megatron-LM`.
-- When rebasing, cherrypicking or commiting, sign the commits with both `-s` and `-S`: `-s` adds the required
-  `Signed-off-by` trailer, and `-S` signs the commit so copy-pr-bot and `/ok to
-test` can verify the pushed commit without manually specifying the SHA.
-Megatron Core engineers at NVIDIA should sign using their NVIDIA emails so they
-are automatically added to the right user groups on the internal Slack
-workspace.
+- When rebasing, cherry-picking or committing, sign the commits with both `-s` and `-S`: `-s` adds the required
+  `Signed-off-by` trailer, and `-S` signs the commit so copy-pr-bot and
+  `/ok to test` can verify the pushed commit without manually specifying the SHA.
+  `/ok to test` is not required for PR authors in `NVIDIA/mcore-engineers` as long as
+  they sign their commits with `-S`.
+- Authors in `NVIDIA/mcore-engineers` should sign using their NVIDIA emails so they
+  are automatically added to the right user groups on the internal Slack
+  workspace.
 - Before merging any PR, check for open PRs whose GitHub base/diffbase is
   `pull-request/<this PR number>`. Retarget every such dependent PR to `main`
   before merging; otherwise GitHub may close it and discard review discussion