fleet-manager ui: label target-version pin as recorded intent (not yet enforced)

Per the option-A decision (deploy current design without per-host versioning):
add an honest note on the Lifecycle panel that kiosk-url/reboot/drain reconcile
via the agent but per-host boot-version assignment (dnsmasq cohort steering) is
not yet wired, so a version pin is stored + pushed but does not change what the
host boots. Avoids implying the pin takes effect.

serving/fleet-manager/ui/src/pages/Lifecycle.svelte

@@ -153,6 +153,11 @@
           {#if okMsg}<span class="pill pill-ok">{okMsg}</span>{:else}<span></span>{/if}
           <button class="btn btn-restricted" disabled={busy} onclick={submit}>{busy ? 'applying…' : '⚿ apply desired state'}</button>
         </div>
+        <p class="mt-3 text-xs leading-relaxed text-faint">
+          Recorded intent — kiosk URL / reboot / drain reconcile via the host agent, but per-host
+          <span class="text-muted">boot-version assignment</span> (dnsmasq cohort steering) is not yet wired,
+          so a version pin is stored and pushed but does not change what the host boots at next reboot.
+        </p>
       </Panel>
     {:else}
       <Panel title="lifecycle control" tag="select a host"><p class="text-sm text-muted">Select a host to set its server-authoritative desired state (version pin, kiosk URL, reboot, drain).</p></Panel>