fix(diagnose): require field on every topk_keys entry

[MrBeldum]

Summary

• Make the topk_keys field requirement explicit: a missing field flags the entry node so path/line are actionable (instead of a nil-node finding).
• Omitting weight stays valid (connector default).
• Table-driven coverage for missing/empty/unknown/valid fields; docs note in DIAGNOSE.md.

Test plan

• go test ./internal/diagnose ./internal/cli
• go vet ./...

Fixes #23

[kwisatzh]

thanks! will review this week.

[kwisatzh]

Thanks! One change before merge: the collector also accepts custom fields in topk_keys (any field defined under fields, e.g. workflow_key), so please drop the list of three names from the docs line and just say each entry needs a field. Also, gofmt will flag the double blank line before TestTopKKeysRequireField.

also, one requirement before merge: we only accept signed commits. Could you sign yours and force-push the branch? With an SSH key that's already on your GitHub account:

git config gpg.format ssh
git config user.signingkey ~/.ssh/id_ed25519.pub
git rebase --exec 'git commit --amend --no-edit -S' origin/main
git push --force-with-lease

Also add the key as a "Signing key" under GitHub → Settings → SSH and GPG keys, so the commits show as Verified. Docs: https://docs.github.com/en/authentication/managing-commit-signature-verification

[kwisatzh]

Thanks for fixing the documentation and formatting! The code and tests look good now.

The remaining blockers are commit signatures and DCO sign-offs. Please update both of your authored commits so each has a verified cryptographic signature and a matching Signed-off-by trailer. These are separate requirements; my earlier instructions covered signing but omitted the sign-off. Adding a new signed commit alone won’t repair the earlier commits.

The setup is in [CONTRIBUTING.md](https://github.com/llm-measurement/fleetdiff/blob/main/CONTRIBUTING.md). Once commit-signatures, dco, and the remaining CI checks pass on the updated branch, this is ready to merge.

[MrBeldum]

Thanks for confirming the code and tests look good, and for clarifying that signatures and DCO sign-offs are separate requirements covering both authored commits.

Noted: both commits still need a verified cryptographic signature plus a matching Signed-off-by trailer. That step is pending on my side — I'll update the branch once it's done, then confirm the commit-signatures, dco, and remaining CI checks pass.

Disclosure: this reply was drafted with AI assistance.