docs(skills): rewrite container-security descriptions to a uniform standard

All 33 container-security skills now carry what it does, an explicit
"Use when" trigger, keywords, and a negative trigger naming the nearest
neighbour. Six collision clusters resolved by differentiating scope
rather than merging, so no skill is removed:

- kube-bench: running the tool vs interpreting findings into an audit
- Calico: portable upstream NetworkPolicy vs Calico-as-CNI vs Calico-only
  CRDs (GlobalNetworkPolicy, HostEndpoint, DNS egress)
- Falco: deploying and operating it vs authoring escape rules
- container escape: tool-agnostic runtime signals vs Falco rule syntax vs
  static posture audit vs offensive breakout
- Trivy: all-target platform and operator vs single-image scan
- Docker: images and Dockerfiles vs daemon.json vs the CIS audit script

Also replaces the templated "When to Use" boilerplate in these files,
including bullets that only restated the skill's own name.

Worst pair (Pod Security Standards vs Pod Security Admission) drops from
0.77 cosine to below the 0.45 threshold. Repo-wide: colliding pairs
60 -> 56, skills involved 105 -> 94.

skills/securing-container-registry-with-harbor/SKILL.md

@@ -1,11 +1,14 @@
 ---
 name: securing-container-registry-with-harbor
-description: Configures the Harbor open-source container registry's security features
-  — integrated Trivy vulnerability scanning, Notary/Cosign image signing and content
-  trust policies, project-level RBAC, immutable tag retention rules, and OIDC authentication
-  — to enforce image provenance and block vulnerable image deployment. Use when deploying
-  or hardening a Harbor registry, or when access control and compliance requirements
-  call for signed, scanned images.
+description: >-
+  Configures the security features of the Harbor open-source container registry - integrated
+  Trivy scanning, Cosign and Notary content trust policies, project-level RBAC, immutable tag
+  and retention rules, and OIDC authentication - to enforce provenance and block deployment of
+  vulnerable images. Use when deploying or hardening Harbor, or when compliance requires that
+  only signed and scanned images can be pulled. Keywords: Harbor, project policy, content
+  trust, immutable tag, retention, robot account, OIDC, replication. Do not use for signing
+  images with Cosign outside a registry - use
+  implementing-image-provenance-verification-with-cosign.
 domain: cybersecurity
 subdomain: container-security
 tags: