Add erasure-coded multi-lane spread foundation.

Server Reed-Solomon 4+2 shard encode on deploy plans when erasure_lanes_enabled; agents reassemble from parallel lane URLs as staging fallback with BGP/Path Tracer hints.

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.erasure_lanes_enabled === true}
+                onChange={(e) => onUpdate('server.erasure_lanes_enabled', e.target.checked)}
+              />
+              <span>Erasure-coded multi-lane spread <HelpTip field="erasure_lanes" /></span>
+            </label>
+          </div>
           {server.lotl_onion_tiers?.length ? (
             <p className="form-hint" style={{ marginTop: '0.75rem' }}>
               Spread tier order: <code className="mono-sm">{server.lotl_onion_tiers.join(' → ')}</code>