fix(group): show all user-created personas in the participant selector (#1770)

_getCharacterList() had two bugs that silently dropped every
user-created persona from the group participant picker:

1. The /api/presets/templates endpoint returns a JSON array directly,
   but the code read `data.templates` (always undefined). The forEach
   over `data.templates || []` iterated over an empty array every time,
   so no user templates were ever added.

2. Even if the array had been read correctly, the `t.isCharacter` guard
   would have filtered them all out — user templates are saved by
   presets.js without that flag, which is only present on built-in
   PROMPT_TEMPLATES entries.

Fix: accept both the direct-array and the {templates:[]} shapes, drop
the isCharacter guard (user_templates are personas by definition), and
use the correct field name (system_prompt, not prompt) so the character
prompt actually reaches the group chat.

Fixes #1656

static/js/group.js

@@ -299,13 +299,16 @@ async function _getCharacterList() {
       });
     }
   } catch (e) {}
-  // Load user templates and wait for them before returning
+  // Load user templates and wait for them before returning.
+  // The endpoint returns a JSON array directly (not {templates:[...]}).
+  // All user templates are personas by definition — no isCharacter filter needed.
   try {
     const r = await fetch(API_BASE + '/api/presets/templates', { credentials: 'same-origin' });
     const data = await r.json();
-    (data.templates || []).forEach(t => {
-      if (t.isCharacter && !chars.find(c => c.id === t.id)) {
-        chars.push({ id: t.id, name: t.name, prompt: t.prompt || '' });
+    const templates = Array.isArray(data) ? data : (data.templates || []);
+    templates.forEach(t => {
+      if (t.id && t.name && !chars.find(c => c.id === t.id)) {
+        chars.push({ id: t.id, name: t.name, prompt: t.system_prompt || t.prompt || '' });
       }
     });
   } catch (e) {}