Labels: show the new label after creating it

Creating a label while the section was collapsed hid the thing you had
just made — the row was added, behind a closed chevron.

Open the section on a successful create, and persist that the same way
the chevron does, so it does not snap shut on the next mount.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018SqJYt7jD7oUEkoY68sBZo

plugins/webmail_plugin_labels/webmail_plugin_labels/ui/sidebar.js

@@ -110,6 +110,10 @@ export default function mount(el, ctx) {
     if (!name) { adding = null; render(); return; }
     await ctx.api.pluginFetch("/labels", { method: "POST", body: JSON.stringify({ name }) });
     adding = null;
+    // Creating a label while the section is collapsed would hide the thing you
+    // just made, so open it — and remember that, the way the chevron does.
+    collapsed = false;
+    try { localStorage.setItem("labels.collapsed", "0"); } catch { /* ignore */ }
     window.dispatchEvent(new Event("webmail:labels-changed"));
   }