Data groups: a provider's models read only their own group's data

Every connection is in a data group. Its models are handed, and can find,
only that group's memories, notes, skills, knowledge, reports and
personality -- by search and by id. A chat stays in the group it was
started in: switching its model, the endpoint fallback, the crowd, friends,
bases and the @ menu all stay inside it, and a chat whose model has moved
is refused rather than sent. A group may name its own embedder and image
reviewer. data.manage lets a person make personal groups, remap
connections for themselves and move their own records.

Also: a search no longer mixes two embedders of the same width.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/lembas/web/templates/admin/_connection_row.html

@@ -72,6 +72,22 @@
       </p>
     </div>
 
+    {# Which data group this provider reads. Only worth a control once there is a
+       second group to choose; until then every connection is in the default one
+       and the field would be a select with one option. #}
+    {% if data_group_choices is defined and data_group_choices|length > 1 %}
+    <div class="field">
+      <label class="field__label" for="group-{{ connection.id }}">{{ t("Data group") }}</label>
+      <select class="select" id="group-{{ connection.id }}" name="data_group_id">
+        {% for group in data_group_choices %}
+        <option value="{{ group.id }}"
+                {{ 'selected' if (connection.data_group_id or 'default') == group.id }}>{{ group.name }}</option>
+        {% endfor %}
+      </select>
+      <p class="field__hint">{{ t("Its models read only this group's memories, notes, skills, knowledge and reports, and a chat started on one of them stays in it. Moving a connection does not move any data: it starts reading the other group.") }}</p>
+    </div>
+    {% endif %}
+
     <div class="field">
       <label class="field__label" for="unload-{{ connection.id }}">{{ t("Unload URL") }}</label>
       <div class="btn-row">