billboard applets: single-root wrapper for HTMX swap; full context on toggle — TDD

- _applets.html wraps menu + container in one #id_billboard_applets_wrapper div; form's hx-target is now the wrapper, so OK no longer leaves a stale duplicate menu in the DOM (which previously caused the next OK to revert prior toggles)
- toggle_billboard_applets passes full context (recent_room, recent_events, viewer, my_rooms) via factored _billboard_context helper, so Most Recent + My Scrolls keep their content after a toggle instead of falling through to the empty fallback
- applets.js: register id_billboard_applets_wrapper as an applet container so post-swap menu cleanup runs
- BillboardAppletsTest: portrait viewport in setUp; FT covers content preservation, no-revert on second toggle, & post-refresh state
- 4 new ITs: Most Recent renders Coin-on-a-String after toggle; My Scrolls renders room name; response has single menu div; second toggle preserves prior hidden state

Code architected by Disco DeDisco <discodedisco@outlook.com>
Git commit message Co-Authored-By:
Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/templates/apps/billboard/_partials/_applets.html

@@ -1,27 +1,29 @@
-<div id="id_billboard_applet_menu" style="display:none;">
-    <form
-        hx-post="{% url "billboard:toggle_applets" %}"
-        hx-target="#id_billboard_applets_container"
-        hx-swap="outerHTML"
-    >
-        {% csrf_token %}
-        {% for entry in applets %}
-            <label>
-                <input
-                    type="checkbox"
-                    name="applets"
-                    value="{{ entry.applet.slug }}"
-                    {% if entry.visible %}checked{% endif %}
-                >
-                {{ entry.applet.name }}
-            </label>
-        {% endfor %}
-        <div class="menu-btns">
-            <button type="submit" class="btn btn-confirm">OK</button>
-            <button type="button" class="btn btn-cancel applet-menu-cancel">NVM</button>
-        </div>
-    </form>
-</div>
-<div id="id_billboard_applets_container">
-    {% include "apps/applets/_partials/_applets.html" %}
+<div id="id_billboard_applets_wrapper">
+    <div id="id_billboard_applet_menu" style="display:none;">
+        <form
+            hx-post="{% url "billboard:toggle_applets" %}"
+            hx-target="#id_billboard_applets_wrapper"
+            hx-swap="outerHTML"
+        >
+            {% csrf_token %}
+            {% for entry in applets %}
+                <label>
+                    <input
+                        type="checkbox"
+                        name="applets"
+                        value="{{ entry.applet.slug }}"
+                        {% if entry.visible %}checked{% endif %}
+                    >
+                    {{ entry.applet.name }}
+                </label>
+            {% endfor %}
+            <div class="menu-btns">
+                <button type="submit" class="btn btn-confirm">OK</button>
+                <button type="button" class="btn btn-cancel applet-menu-cancel">NVM</button>
+            </div>
+        </form>
+    </div>
+    <div id="id_billboard_applets_container">
+        {% include "apps/applets/_partials/_applets.html" %}
+    </div>
 </div>