Add Fleet Torrent erasure extension with shard DHT and gossip.

Content-addressed shard DHT on seeder agents with subnet_primary_seeder election, cross-subnet fleet_torrent_gossip, BGP swarm magnets, C2 torrent manifest, and k-of-n peer fetch with C2 fallback.

server/web/src/components/CalibrationAIControl.tsx

@@ -195,6 +195,17 @@ export default function CalibrationAIControl({ server, onUpdate }: Props) {
               <span>Enable adaptive strategy engine <HelpTip field="adaptive_strategy" /></span>
             </label>
           </div>
+          <div className="form-group checkbox-group" style={{ marginTop: '0.5rem' }}>
+            <label className="checkbox-label">
+              <input
+                type="checkbox"
+                className="checkbox"
+                checked={server.fleet_torrent_enabled === true}
+                onChange={(e) => onUpdate('server.fleet_torrent_enabled', e.target.checked)}
+              />
+              <span>Fleet Torrent (shard DHT + gossip) <HelpTip field="fleet_torrent" /></span>
+            </label>
+          </div>
           <div className="form-group checkbox-group" style={{ marginTop: '0.5rem' }}>
             <label className="checkbox-label">
               <input

server/web/src/components/Fleet/AccessDepthPanel.css

@@ -10,6 +10,19 @@
   margin-bottom: 0.5rem;
 }
 
+.access-depth-oath-link {
+  margin-left: auto;
+  font-size: 0.68rem;
+  letter-spacing: 0.08em;
+  text-transform: uppercase;
+  color: var(--text-muted, #8899aa);
+  text-decoration: none;
+}
+
+.access-depth-oath-link:hover {
+  color: var(--neon-cyan, #00e8f5);
+}
+
 .access-depth-grid {
   display: grid;
   grid-template-columns: repeat(auto-fit, minmax(11rem, 1fr));

server/web/src/components/Fleet/AccessDepthPanel.tsx

@@ -188,6 +188,9 @@ export default function AccessDepthPanel({ agent, diagnostics }: Props) {
           </span>
         )}
         {!policyLoaded && <span className="access-depth-muted">loading policy…</span>}
+        <Link to="/oath" className="access-depth-oath-link" title="Immutable operator accountability ledger">
+          Oath
+        </Link>
       </div>
 
       <div className="access-depth-grid">