[operations] Add runbook for fuzz-mdx.yml silent-failure monitoring

[kubestellar-hive]

What

Adds runbooks/fuzz-mdx-monitoring.md, documenting how to manually detect and recover from a silently-failed weekly run of .github/workflows/fuzz-mdx.yml (the MDX sanitizer fuzz harness).

Why

Fixes the gap tracked in #6805: fuzz-mdx.yml's only if: failure() step uploads a 14-day crash-log artifact — it never opens or updates a tracking issue, unlike generate-leaderboard.yml/generate-acmm-history.yml in this repo. A crash on the unattended weekly scheduled run (as opposed to a PR check) can go unnoticed indefinitely, and the reproduction evidence (crash seed/log) is deleted after 14 days. This follows the same pattern already used for runbooks/scorecard-monitoring.md (#6724) and runbooks/stale-workflow-monitoring.md (#6729).

The workflow-side if: failure() alert fix itself is out of scope for this PR — it requires workflows permission that agent tokens do not have, so a maintainer needs to add it directly to .github/workflows/fuzz-mdx.yml. This runbook is the bounded, non-workflow mitigation in the meantime.

Scope

Docs-only change (new file under runbooks/). No workflow, alert, or code behavior is modified.

Closes: partially addresses #6805 (manual mitigation; workflow fix still needs a maintainer).

— hive: agent=operations backend=copilot model=claude-sonnet-4-6

[kubestellar-hive]

Important

Held for human sign-off on the direction, not on the code.

This PR's only tracked rationale is #6805, which the hive filed itself — issue #6805 was filed by kubestellar-hive[bot] and no human has acknowledged it. An agent-filed issue does not, on its own, establish that anyone agreed to the direction (hivecommons/hive#5117).

The change may well be right; nothing here is a review of it. To release the hold, acknowledge the direction on that issue — comment on it, assign yourself, or add the approved-direction label — and remove the hold label here.

[kubestellar-prow]

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[kubestellar-prow]

Hi @kubestellar-hive[bot]. Thanks for your PR.

I'm waiting for a kubestellar member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[kubestellar-hive]

Closing: superseded by runbooks/fuzz-mdx-failure-detection.md, already merged to main in #6808 documenting this exact fuzz-mdx.yml silent-failure gap. Adding a second differently-named runbook (fuzz-mdx-monitoring.md) for the same gap would create duplicate/conflicting docs. See #6856.

🐝 Hive Agent: operations | Instance: hosted-kubestellar-console-4vkt | SHA: 989d40c5

— hive: agent=operations backend=copilot model=claude-sonnet-4-6