dashboard: K3PT ST4T3 section + agent links open in new tab

new section between containers and questions: lists every name with a
state dir under /var/lib/hyperhive/agents/ that doesn't correspond to
a live container. shows state size + last-modified age + whether
claude creds are kept. two actions per row:

- R3V1V3 — queues a spawn approval with the same name (operator
  approves to recreate; spawn flow reuses prior config + claude
  creds, no re-login needed)
- PURG3 — wipes the agent's state + applied dirs (post /purge-tombstone/
  endpoint; refuses if a live container with that name still exists)

dashboard also opens agent links in new tabs now (target=_blank +
rel=noopener) so the operator's overview tab stays put when they
dive into an agent.

hive-c0re/assets/index.html

@@ -16,6 +16,12 @@
     <p class="meta">loading…</p>
   </div>
 
+  <h2>◆ K3PT ST4T3 ◆</h2>
+  <div class="divider">══════════════════════════════════════════════════════════════</div>
+  <div id="tombstones-section">
+    <p class="meta">loading…</p>
+  </div>
+
   <h2>◆ M1ND H4S QU3STI0NS ◆</h2>
   <div class="divider">══════════════════════════════════════════════════════════════</div>
   <div id="questions-section">