docs(seal-check): record k3d/k3s NetworkPolicy substrate verification (backend#1184)

[LukasWodka]

Summary

Records the k3d/k3s NetworkPolicy substrate verification that RFC-0003 §8.4 explicitly demands ("do not assume k3d enforces NetworkPolicy"). Docs-only — one file.

What was run

On a throwaway k3d v5.8.3 cluster (k3s v1.33.6+k3s1), a standalone deny-egress NetworkPolicy (podSelector on a probe pod, policyTypes: [Egress], empty egress:) was applied and a curl from the pod to 1.1.1.1:443 was measured across three states:

state	result
no policy (baseline)	reachable — HTTP 301
deny-egress policy applied	BLOCKED — connect failure (egress dropped)
policy removed (control)	reachable again — HTTP 301

The reachable → blocked → reachable transition makes the block attributable to the policy, not a fluke or an image-pull artifact. So k3s's embedded (kube-router) controller does enforce egress NetworkPolicy on this k3d version — flannel handles pod networking, but the netpol controller is active and enforcing.

Honest scope (deliberately precise)

This verifies the substrate primitive — the specific doubt §8.4 raises. It is not the full-chart egress-enforcement probe run against a deployed release; that end-to-end run stays open under backend#1184, and I've kept the §8.3 k3d cell reading "substrate verified; full-probe run pending" rather than overclaiming "sealed".

Why it matters

The chart's egress-enforcement seal-check relies on the CNI actually dropping egress. That reliance was documented-but-unverified ("expected is not verified"). It's now verified for the k3d/k3s substrate, so the local-dev "nothing gets out" guarantee rests on measured behavior, not an assumption.

Epic: backend#1151 · Ticket: backend#1184 (D12)

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Note

Low Risk
Documentation-only change to seal-check status and runbook text; no runtime, chart, or security behavior changes.

Overview
docs/SEAL-CHECK.md now records a completed k3s egress NetworkPolicy substrate check on k3d v5.8.3 / k3s v1.33.6+k3s1 (2026-07-30): deny-egress policy produced reachable → blocked → reachable again on curl to 1.1.1.1:443, with that evidence centralized in the §8.4 Status note.

The §8.3 k3d matrix cell and follow-ups are updated to substrate verified; full-chart egress-enforcement probe still pending, so k3d remains unsealed for the egress guarantee until the deployed-release runbook (steps 1–4) is recorded—without overclaiming sealed status.

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[LukasWodka]

👋 Heads-up — Code review queue is at 33 / 30

Above the WIP limit. The team convention is to review existing PRs before opening new work.

Open PRs currently in Code review (oldest first):

• backend#1146 — docs(rfc): platform cost & autoscaling architecture · author: @saadqbal · reviewer: @LukasWodka, @saqlainsyed007, @aptracebloc
• backend#1201 — docs(rfc): Data spaces & federated dataset composition (draft) · author: @LukasWodka · reviewer: @saadqbal
• backend#1217 — docs(rfc): Dataset integrity & score reproducibility (draft) · author: @LukasWodka · reviewer: @saadqbal
• backend#1261 — RFC-BACKEND-0008: board & process reset (decision RFC — for markup) · author: @LukasWodka · reviewer: @saadqbal
• backend#1284 — docs(deploy): backend deploy runbook skeleton (#1263) · author: @LukasWodka · no reviewer assigned
• backend#1332 — feat(check-model): allow KNN/GaussianProcess on a single-edge owned dataset (#923 follow-up) · author: @divyasinghds · no reviewer assigned
• backend#1353 — chore(ci): baseline historical gitleaks findings + wire caller · author: @LukasWodka · no reviewer assigned
• backend#1361 — feat(tasks): bound ExperimentQueue growth for PAUSED experiments (backend#1351) · author: @saqlainsyed007 · no reviewer assigned
• backend#1368 — feat(blob_store): migrate CheckModelClassesView link/model_reform to blob_store (#1162) · author: @saadqbal · no reviewer assigned
• claude-skills#14 — feat(skill): add tracebloc-frontend-app skill · author: @waqaskhanroghani · reviewer: @saadqbal

Pull from review before opening new work. (This is a nudge from the kanban WIP check, not a block.)

[saqlainsyed007]

Docs-only review of docs/SEAL-CHECK.md. The experiment itself is sound and honestly scoped (curl to an IP so no DNS is needed; reachable→blocked→reachable proves attribution). But the change asserts an edit to the §8.3 matrix cell that it never actually makes, leaving the document self-contradictory. Details inline.

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[LukasWodka]

Thanks — all three addressed in b30bdf9:

• #i — updated the §8.3 k3d matrix cell to "Substrate verified; full-probe run pending", matching the prose that cross-references it. That was the concrete edit the PR promised but never made — the document is no longer self-contradictory.
• #ii — the Status note now leads with "still UNSEALED for the egress guarantee on k3d until the full-chart probe is recorded", so the bold VERIFIED can't be skimmed as "sealed". The distinction (probe-pod netpol, not the chart's training-labelled selector) is stated up front.
• #iii — the run evidence (versions + reachable→blocked→reachable) is now stated once in the Status note; the post-runbook paragraph, the follow-ups bullet, and the matrix cell reference it — which is how the cell drifted in the first place.

[saqlainsyed007]

All three review findings addressed in b30bdf9:

1. §8.3 k3d matrix cell now reads "substrate verified; full-probe run pending" — matches the prose that references it; self-contradiction resolved.
2. Status block now leads with the explicit "still UNSEALED for the egress guarantee on k3d" framing, restoring the doc's "never silently sealed" philosophy.
3. Evidence now lives in a single record (the §8.4 Status note); the post-runbook paragraph and follow-ups reference it instead of restating.

Clean, root-cause fixes.

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[LukasWodka]

/fr-pass