Roll back stored settings when a creation fails, and keep form ids unique

create_agent puts back the caps and inference settings it replaced if a
later store or the job insert fails, so a refused creation leaves nothing
behind for the name. The shared field components take an id prefix so the
create dialog and an open editor never share a DOM id. The queue check now
follows the hive roster check, the 422 is documented, and the copy says
empty rather than closed and that destroy keeps stored settings.

frontend/packages/swarm-ui/src/agent/detail/AgentInference.tsx

@@ -141,36 +141,40 @@ export function draftBody(d: InferenceDraft): Settings {
 export function InferenceFields({
   draft,
   onChange,
+  idPrefix = "inference",
 }: {
   draft: InferenceDraft;
   onChange: (d: InferenceDraft) => void;
+  // Ids must be unique on the page, and the agents page can hold the editor
+  // and the create dialog at once.
+  idPrefix?: string;
 }) {
   const problem = draftProblem(draft);
   return (
     <>
       <TextField
-        id="inference-model"
+        id={`${idPrefix}-model`}
         label="model"
         value={draft.model}
         placeholder="e.g. opus"
         onInput={(model) => onChange({ ...draft, model })}
       />
       <SelectField
-        id="inference-effort"
+        id={`${idPrefix}-effort`}
         label="effort"
         value={draft.effort}
         options={EFFORT_OPTIONS}
         onChange={(effort) => onChange({ ...draft, effort })}
       />
       <TextField
-        id="inference-subagent-models"
+        id={`${idPrefix}-subagent-models`}
         label="subagent models"
         value={draft.subagents}
         placeholder="e.g. haiku, sonnet"
         onInput={(subagents) => onChange({ ...draft, subagents })}
       />
       <TextField
-        id="inference-max-subagents"
+        id={`${idPrefix}-max-subagents`}
         label="max subagents"
         value={draft.maxSubagents}
         placeholder="empty for no cap"

frontend/packages/swarm-ui/src/agent/detail/AgentLimits.tsx

@@ -50,16 +50,20 @@ export function LimitsFields({
   memory,
   onCpu,
   onMemory,
+  idPrefix = "limits",
 }: {
   cpu: string;
   memory: string;
   onCpu: (v: string) => void;
   onMemory: (v: string) => void;
+  // Ids must be unique on the page, and the agents page can hold the editor
+  // and the create dialog at once.
+  idPrefix?: string;
 }) {
   return (
     <>
       <TextField
-        id="limits-cpu-quota"
+        id={`${idPrefix}-cpu-quota`}
         label="cpu quota"
         value={cpu}
         placeholder="e.g. 400%"
@@ -69,7 +73,7 @@ export function LimitsFields({
         A percentage of one core: 100% is one core, 400% is four.
       </p>
       <TextField
-        id="limits-memory-max"
+        id={`${idPrefix}-memory-max`}
         label="memory max"
         value={memory}
         placeholder="e.g. 8G"

frontend/packages/swarm-ui/src/pages/CreateAgentForm.tsx

@@ -167,8 +167,8 @@ export function CreateAgentForm({
           <p class="create-agent-intro">
             Create a new agent's swarm-level identity. This only queues the job
             — check <Link href="/jobs">jobs</Link> to watch it settle. Resource
-            caps and inference are optional; leave them closed to keep the
-            defaults.
+            caps and inference are optional; leave them empty to set nothing. A
+            name set up before keeps the settings stored for it.
           </p>
           {hivesError && (
             <ApiErrorPanel
@@ -206,6 +206,7 @@ export function CreateAgentForm({
               <summary>resource caps</summary>
               <div class="create-agent-section-body">
                 <LimitsFields
+                  idPrefix="create-limits"
                   cpu={cpu}
                   memory={memory}
                   onCpu={setCpu}
@@ -216,7 +217,11 @@ export function CreateAgentForm({
             <details class="create-agent-section">
               <summary>inference</summary>
               <div class="create-agent-section-body">
-                <InferenceFields draft={inference} onChange={setInference} />
+                <InferenceFields
+                  idPrefix="create-inference"
+                  draft={inference}
+                  onChange={setInference}
+                />
               </div>
             </details>
             <Button