fix: generate client-side id for optimistic update, return shallow copy from getUserTemplates

1. New characters now get a 'user-<hex>' id immediately on save, matching
   the server's convention (uuid.uuid4().hex[:8]). Previously the id was ''
   which the merge guard in _getCharacterList filtered as falsy.

2. getUserTemplates() now returns [...userTemplates] so callers cannot
   accidentally mutate module state.

Author: michaelxer

static/js/presets.js

@@ -837,7 +837,7 @@ export async function saveCustomPreset(showToast, showError) {
       if (saveName) {
         const _existing = userTemplates.find(t => t.name === saveName);
         const _entry = {
-          id: (_existing && _existing.id) || '',
+          id: (_existing && _existing.id) || ('user-' + Math.random().toString(16).slice(2, 10)),
           name: saveName,
           system_prompt: system_prompt || '',
           temperature: config.temperature,
@@ -906,7 +906,7 @@ export function getAllPresets() {
  * Get the in-memory user templates list (may be stale; call loadUserTemplates first if freshness matters).
  */
 export function getUserTemplates() {
-  return userTemplates;
+  return [...userTemplates];
 }
 
 /**

tests/test_group_character_dropdown.py

@@ -48,5 +48,13 @@ def test_presets_optimistic_update_on_save():
 
 
 def test_presets_getUserTemplates_returns_array():
-    """getUserTemplates should return the userTemplates array directly."""
-    assert "return userTemplates" in PRESETS_JS
+    """getUserTemplates should return a shallow copy of userTemplates."""
+    assert "return [...userTemplates]" in PRESETS_JS
+
+
+def test_presets_optimistic_id_not_empty():
+    """Optimistic update must generate a client-side id for new characters (not empty string)."""
+    # The id generation uses 'user-' prefix matching server's uuid convention
+    assert "user-' + Math.random" in PRESETS_JS
+    # Must NOT use empty string as fallback (that was the bug)
+    assert "(_existing && _existing.id) || ''" not in PRESETS_JS