[verified] fix debrief pain display ([object Object]) + add 'create persona from this one' button

- formatValue(): render arrays of objects (e.g. pains) as readable text
  instead of '[object Object], [object Object]'
- SessionDetail: new 'สร้างบุคคลต้นแบบจากต้นแบบนี้' button calls the
  existing group persona-variant endpoint so trainees/orders can regenerate
  a persona based on the revealed one after a session

frontend/src/views/SessionDetail.vue

@@ -45,6 +45,16 @@
             </div>
           </div>
         </details>
+
+        <button
+          v-if="session.group_id && session.persona_id"
+          class="soft variant-btn"
+          @click="makeVariant"
+          :disabled="creating"
+        >
+          {{ creating ? i18n.t('creating') : i18n.t('createVariant') }}
+        </button>
+        <div v-if="variantMsg" class="muted" style="margin-top:8px">{{ variantMsg }}</div>
       </div>
     </template>
   </div>
@@ -52,14 +62,17 @@
 
 <script setup>
 import { computed, onMounted, ref } from 'vue'
-import { useRoute } from 'vue-router'
+import { useRoute, useRouter } from 'vue-router'
 import { api } from '../api'
 import { i18n } from '../i18n'
 
 const route = useRoute()
+const router = useRouter()
 const session = ref(null)
 const loading = ref(true)
 const error = ref('')
+const creating = ref(false)
+const variantMsg = ref('')
 
 const statusClass = computed(() => session.value?.status === 'active' ? 'active' : session.value?.outcome || 'not_tried')
 const statusLabel = computed(() => {
@@ -80,11 +93,43 @@ function fieldLabel(key) {
   return labels[key] || key
 }
 function formatValue(value) {
-  if (Array.isArray(value)) return value.join(', ')
+  if (Array.isArray(value)) {
+    // Arrays may hold plain strings OR objects (e.g. pains [{title,description}]).
+    // Never let join() stringify an object into "[object Object]".
+    return value
+      .map((item) => {
+        if (item && typeof item === 'object') {
+          const readable = item.description ?? item.title ?? item.text
+          return readable && typeof readable === 'string' && readable.trim()
+            ? readable.trim()
+            : JSON.stringify(item)
+        }
+        return String(item)
+      })
+      .join(', ')
+  }
   if (value && typeof value === 'object') return JSON.stringify(value)
   return String(value == null ? '—' : value)
 }
 
+async function makeVariant() {
+  if (!session.value?.group_id || !session.value?.persona_id) return
+  creating.value = true
+  variantMsg.value = ''
+  try {
+    const created = await api.createPersonaVariant(session.value.group_id, session.value.persona_id)
+    const target = created && typeof created === 'object' && created.group_id
+      ? created.group_id
+      : session.value.group_id
+    // Trainee variants land in the private group; admin variants in the shared group.
+    await router.push(`/groups/${target}/personas`)
+  } catch (e) {
+    variantMsg.value = i18n.t('requestFailed')
+  } finally {
+    creating.value = false
+  }
+}
+
 onMounted(async () => {
   try {
     session.value = (await api.getSession(route.params.sid)).session
@@ -101,6 +146,7 @@ onMounted(async () => {
 .bubble { max-width:72%; padding:10px 14px; white-space:pre-wrap; word-break:break-word; }
 .msg-system { align-self:center; background:#fef3c7; color:#92400e; font-size:12px; max-width:88%; border-radius:999px; }
 .debrief { margin-top:16px; }
+.variant-btn { margin-top:14px; }
 .reveal-grid { display:grid; grid-template-columns:1fr 1fr; gap:8px; margin-top:8px; }
 .rev { display:flex; flex-direction:column; background:#f8fafc; border:1px solid var(--border); border-radius:8px; padding:8px 10px; }
 .rk { font-size:12px; color:var(--muted); }