feat(call2): short/long desc structure in seed (not brand voice)

Call 2 seed now requires benefit-first short + four-part long HTML, returned
as JSON. POST parses and persists both fields; Create-desc gate no longer
requires short (Call 2 writes it). Brand voice/geo stay Settings-injected.

frontend/src/create/inference/GenerateText.svelte

@@ -3,6 +3,7 @@
   let contentEnabled = false;
   let reachable = false;
   let description: string | null = null;
+  let shortDescription: string | null = null;
   let error = '';
   let busy = false;
 
@@ -29,10 +30,14 @@
     busy = true;
     error = '';
     description = null;
+    shortDescription = null;
     try {
       const res = await fetch(`/api/v1/slabs/${encodeURIComponent(slabId)}/inference/call2`, { method: 'POST' });
       const body = await res.json();
-      if (res.ok) description = body.description;
+      if (res.ok) {
+        description = body.description;
+        shortDescription = body.short_description ?? null;
+      }
       else error = body.error?.message || `call2 failed (${res.status})`;
     } catch {
       error = 'network error';
@@ -61,7 +66,8 @@
       <button on:click={generate} disabled={busy}>{busy ? 'Working…' : 'Generate description (Call 2)'}</button>
     </div>
     {#if error}<p class="err">{error}</p>{/if}
-    {#if description}<p class="desc">{description}</p>{/if}
+    {#if shortDescription}<p class="desc"><strong>Short:</strong> {shortDescription}</p>{/if}
+    {#if description}<p class="desc"><strong>Long:</strong> {description}</p>{/if}
   {/if}
   <button class="mini" on:click={checkReadiness}>Recheck readiness</button>
 </div>