feat(v2/nav): expand quick-nav with ten principal topic flagships

Adds the principal topic flagships to the slim quick-nav bar so the most
relevant destinations across all of Nubenetes are reachable in one click from
any page:

  - Cloud-native pillars: Kubernetes, Docker, GitOps, Terraform,
    K8s Security, Observability
  - Ops disciplines: SRE, DevOps
  - Data/messaging: Message Queue
  - AI/ML: MLOps (next to the existing AI & MCP hub)

Layout groups discovery/meta hubs (Topic Map, Intelligence Digest, Video Hub),
then the pillar + ops + messaging topics, then the AI hubs (AI & MCP, MLOps) and
Methodology, with V1 Archive muted at the far right — 16 curated destinations
total, still under the 18-tab overflow line the bar was designed to avoid.
Reuses the existing .nb-quicknav__link styling (flex-wrap handles density on
narrow viewports); template-only, no CSS change, no page regeneration, V2-only.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/overrides/main.html

@@ -9,6 +9,11 @@
   block, which is empty here since navigation.tabs is disabled). Gives the key
   cross-cutting destinations a persistent, one-click home — without the
   18-tab overflow and without collapsing the full left navigation tree.
+
+  Layout: discovery/meta hubs, then the cloud-native pillar topics
+  (orchestration · containers · delivery · infra · security · observability)
+  plus the ops disciplines (SRE · DevOps), then the AI hubs (AI & MCP · MLOps)
+  and Methodology, with V1 Archive muted at the far right.
 -#}
 {% block tabs %}
 <nav class="nb-quicknav" aria-label="Quick navigation">
@@ -16,7 +21,17 @@
     <a class="nb-quicknav__link" href="/topic-map/">🗺️ Topic Map</a>
     <a class="nb-quicknav__link" href="/tech-digest/">📊 Intelligence Digest</a>
     <a class="nb-quicknav__link" href="/videos/">🎥 Video Hub</a>
+    <a class="nb-quicknav__link" href="/kubernetes/">☸️ Kubernetes</a>
+    <a class="nb-quicknav__link" href="/docker/">🐳 Docker</a>
+    <a class="nb-quicknav__link" href="/gitops/">🔄 GitOps</a>
+    <a class="nb-quicknav__link" href="/terraform/">🏗️ Terraform</a>
+    <a class="nb-quicknav__link" href="/kubernetes-security/">🔐 K8s Security</a>
+    <a class="nb-quicknav__link" href="/monitoring/">📈 Observability</a>
+    <a class="nb-quicknav__link" href="/sre/">🛠️ SRE</a>
+    <a class="nb-quicknav__link" href="/devops/">♾️ DevOps</a>
+    <a class="nb-quicknav__link" href="/message-queue/">📨 Message Queue</a>
     <a class="nb-quicknav__link" href="/ai-agents-mcp/">🤖 AI &amp; MCP</a>
+    <a class="nb-quicknav__link" href="/mlops/">🧠 MLOps</a>
     <a class="nb-quicknav__link" href="/methodology/">📐 Methodology</a>
     <a class="nb-quicknav__link nb-quicknav__link--muted" href="/v1/">📚 V1 Archive</a>
   </div>