docs: update stale Go version requirement and prometheus-operator links

[archy-rock3t-cloud]

• Change is not relevant to the end user.

Changes

Update Go requirement from 1.18+ to 1.26+ to match go.mod. Update coreos/prometheus-operator links to prometheus-operator/prometheus-operator. Add missing workflows to Go version change guide, fix .promu.yaml → .promu.yml.

Verification

Checked go.mod and GitHub org redirect.

[archy-rock3t-cloud]

Expanded scope to also fix 3 dead external links that were causing the Documentation check to fail across multiple thanos PRs:

• grafana.com/docs/loki/latest/clients/promtail/configuration (404 — Loki docs reorganized; Promtail is EOL as of March 2026 and the /clients/... paths no longer exist on /latest/. Pinned to versioned archive: grafana.com/docs/loki/v3.5.x/send-data/promtail/configuration)
• grafana.com/docs/loki/latest/clients/promtail/scraping (404 — same redirect to versioned archive)
• docs.lightstep.com/docs/create-and-use-access-tokens (403 — replaced with /docs/create-and-manage-access-tokens, which is the current "Manage access tokens" page on the post-acquisition Cloud Observability docs)

Verified replacement URLs return HTTP 200 via curl -I -L. make check-docs runs cleanly on the changed lines locally (no mdox link errors).

Also included a small fix on top: docs/components/receive.md had stale mdox-exec output (the snippet from pkg/receive/handler.go lines 1068-1078 had been updated upstream but the doc wasn't regenerated). This was failing the Documentation check independently across PRs.

This should also unblock the docs check on companion PRs #8734, #8737, #8738, #8739, #8743 once they pick up the rebased main.

[kunalworldwide]

Docs fixes look good:

• .promu.yaml → .promu.yml typo fix ✓
• Go 1.18+ → 1.26+ version update ✓
• coreos/prometheus-operator → prometheus-operator/prometheus-operator org rename ✓
• promtail link update to versioned docs ✓
• Added mixin.yaml and codeql-analysis.yml to the Go version update checklist ✓

One thing: might be worth double-checking that the promtail link (grafana.com/docs/loki/v3.5.x/...) isn't itself about to go stale — Grafana tends to remove old versioned docs paths. The latest path would be more durable, though I can see the argument for pinning to a version that matches the proposal's timeframe.

Otherwise LGTM. This has been sitting for a while — would be good to get it merged.

[archy-rock3t-cloud]

@kunalworldwide thanks for the feedback.

latest isn't viable here. Promtail reached EOL in March 2026 and Grafana removed its docs from /latest entirely (superseded by Alloy), so it 404s on both the old and the current path layout. Only the pinned archive still serves these pages:

• https://grafana.com/docs/loki/latest/clients/promtail/scraping/ -> 404
• https://grafana.com/docs/loki/latest/send-data/promtail/scraping/ -> 404
• https://grafana.com/docs/loki/v3.5.x/send-data/promtail/scraping/ -> 200

Fair point that versioned paths do get pruned eventually. If v3.5.x ever goes too, the right fix is to drop the promtail reference and describe the relabel semantics inline rather than repoint at another dead URL, since there's no live upstream page left to link once a component is EOL. For now v3.5.x is the only thing that resolves.

Rebased onto main, so the conflict's cleared and the docs check is green.

[kunalworldwide]

Docs-only cleanup, all looks correct:

• .promu.yml spelling fix matches the actual file name in the repo.
• Go 1.26+ matches go.mod.
• coreos/prometheus-operator → prometheus-operator/prometheus-operator links are the right target (GitHub redirects still work but the direct links are better).
• Promtail relabeling links point to the current Loki docs path.
• Lightstep access-token link also resolves.

No code changes, so the risk is minimal. LGTM.