docs: require PRs to state what was not tested on a real node

[lockwobr]

Description

CI's e2e suites run on kind, whose nodes are containers sharing the runner's kernel. Nothing in CI performs a real reboot: the reboot interrupts under k8s-tests/chainsaw/ run the agentless image, which never touches the host, and the real-agent suite (k8s-tests/operator-agent/) uses only noop interrupts. Systemd shutdown ordering, kernel module and driver installs, GPU workloads, and drains of real workloads are equally out of reach.

Nothing told contributors or agents this. AGENTS.md described kind as "a real cluster", and the PR template's only testing item was "New or existing tests cover these changes." PRs touching host-level paths therefore list unit and kind results, and a reviewer can't tell which claims were verified on a node and which were only reasoned about. #673 is a recent example: its claim that a systemd-terminated reboot still reports success is sound, but the description doesn't say it rests on unit tests and reasoning rather than a real reboot.

This PR makes that explicit without making real-hardware testing mandatory:

• .github/PULL_REQUEST_TEMPLATE.md: a new Testing section (unit / kind e2e / real node) with a Not exercised line. "Nothing" is a valid answer, but a blank one isn't.
• AGENTS.md (.claude/CLAUDE.md): a rule in the Tests section listing what kind can't exercise, and saying that PRs touching those paths must state what ran on a real node. It also corrects the "real cluster" wording.
• CONTRIBUTING.md: the same guidance for human contributors, next to the existing note on running the suites locally.

Testing

• Unit tests
• e2e on kind (CI or local)
• Real node:

Not exercised: Nothing to run. This is a docs and template change only.

Checklist

• I am familiar with the Contributing Guidelines.
• My commits are signed off per the DCO and cryptographically signed: git commit -s -S.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

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📝 Walkthrough

Walkthrough

The changes clarify that Chainsaw runs on kind and describe the real-node behavior it does not cover. Contributor and agent guidance asks authors to report real-node test conditions and untested scenarios for relevant changes. The pull request template adds prompts for unit tests, kind e2e tests, and real-node testing.

Estimated code review effort: 2 (Simple) | ~5 minutes

Suggested reviewers: ayuskauskas

Merge Risk: 🔵 Low · up to f7377

Authors may leave reviewers without real-node coverage details for on_host changes. This is a bounded documentation gap, and adding the trigger is advisable before merge.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: requiring pull requests to state what was not tested on a real node.
Description check	✅ Passed	The description directly explains the documentation and pull request template changes, their purpose, and the testing scope.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Commit to this branch
• Create a new PR

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Actionable comments posted: 1

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Inline comments:
In @.github/PULL_REQUEST_TEMPLATE.md:
- Line 6: Update the Testing guidance in the PR template and contributor
guidance to explicitly include `on_host` step execution as a trigger for
reporting real-node coverage, alongside the existing host-impacting paths.

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📥 Commits

Reviewing files that changed from the base of the PR and between ddcebbb and f73778e.

📒 Files selected for processing (3)

• .claude/CLAUDE.md
• .github/PULL_REQUEST_TEMPLATE.md
• CONTRIBUTING.md

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