feat(root): add Kubernetes security curriculum

Four new modules, moving ROOT 09 off PLANNED and building the
22-scenario CKS-style bank into a coherent course instead of
disconnected exam tasks — see docs/ROOT_CURRICULUM_COVERAGE_MATRIX.md
for the CORE/GUIDED/INDEPENDENT/ADVANCED/ASSESSMENT-BANK classification
behind every placement.

root-09-m01-security-model-and-securitycontext — READY, full
gold-standard pattern: defense in depth, least privilege, hardening a
Pod with SecurityContext. Lesson, demonstration (a Pod before/after
hardening), knowledge check, guided exercise (a hardening checklist),
real Labs (CORE: non-root/drop-capabilities/read-only-fs/
pod-security-context; GUIDED: seccomp; ADVANCED: AppArmor; INDEPENDENT:
the generic pod-security-context duplicate), and a reflection.

root-09-m02-serviceaccounts-and-rbac — PARTIAL: workload identity and
least-privilege permissions. Lesson + knowledge check + real Labs.

root-09-m03-network-and-supplychain-security — PARTIAL: NetworkPolicy
as a security control (default-deny), image/registry trust, TLS
ingress. Lesson + knowledge check + real Labs.

root-09-m04-cluster-hardening-and-runtime — PARTIAL, deliberately
survey-depth: Pod Security Admission and a lighter treatment of
audit-policy/runtime-sandboxing topics that don't belong in the core
daily-driver path.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

content/root/root-09-kubernetes-security/m02-serviceaccounts-and-rbac/02-knowledge-check.md

@@ -0,0 +1,44 @@
+# Knowledge Check: ServiceAccounts & RBAC
+
+---
+
+**1. A Pod is created with no ServiceAccount specified. What identity does it actually run as,
+and what can that identity do by default?**
+
+*Answer:* The `default` ServiceAccount in its Namespace, which by default has essentially no
+permissions — it can authenticate to the API but is granted nothing until an RBAC binding says
+otherwise.
+
+---
+
+**2. You create a Role granting `get`/`list` on Pods, but a workload still can't read Pods.
+What's the most likely missing piece?**
+
+*Answer:* A RoleBinding (or ClusterRoleBinding) connecting that Role to the workload's actual
+ServiceAccount. A Role by itself grants nothing to anyone — it has to be bound to an identity.
+
+---
+
+**3. True or false: a ClusterRole can only ever be applied cluster-wide.**
+
+*Answer:* False. A ClusterRole can be bound via a RoleBinding to apply within just ONE
+Namespace (reusing a cluster-wide-DEFINED permission set in a namespace-SCOPED way), or via a
+ClusterRoleBinding to apply cluster-wide. The Role-type and Binding-type are independent
+choices.
+
+---
+
+**4. Why would a security review flag a Role granting `verbs: ["*"]` on `resources: ["*"]`
+even if the workload "seems to work fine"?**
+
+*Answer:* That grant is root-equivalent API access — it violates least privilege regardless of
+whether the workload happens to only use a small subset of it today. "Works fine" doesn't mean
+"correctly scoped" — an over-broad grant is a real risk the moment that workload (or its
+credentials) is compromised, whether or not it's ever exploited in practice.
+
+## Instructor Notes
+
+**Facilitation:** Question 4 is worth discussing even if everyone answers correctly — the "it
+works, so what's the problem" instinct is exactly what least-privilege review exists to counter.
+
+**Approximate timing:** 5 minutes.