Give the sitemap its own view, with collapse and descendant counts

Extracted from admin#index's inline table into NodesController#sitemap.
Nested <details>/<summary> per branch, one linear pass over the
existing flat [node, level] list (no added queries) -- each node's own
descendant count computed the same way, via a small stack rather than
re-walking the tree per node. Branches under updates/, club/erfas,
club/chaostreffs, and disclosure start collapsed by default
(CccConventions::SITEMAP_COLLAPSED_PATHS); any branch currently
collapsed, whether by that default or because someone just closed it,
is highlighted via a plain :not([open]) selector -- no state tracked
outside the DOM itself.

Dropped the update?-post exclusion this view used to rely on -- no
longer needed now that updates/ collapses instead of being filtered
out, so its real children (previously silently absent) now show up
correctly. admin#index's own, separate @sitemap query is unchanged;
that view has no collapse mechanism to compensate and wasn't part of
this.

1 files changed, 1 insertions, 0 deletions

diff --git a/lib/ccc_conventions.rb b/lib/ccc_conventions.rb
index b420452..352dd3c 100644
--- a/lib/ccc_conventions.rb
+++ b/lib/ccc_conventions.rb
@@ -1,6 +1,7 @@
 module CccConventions
   ERFA_PARENT_NAME       = "club/erfas"
   CHAOSTREFF_PARENT_NAME = "club/chaostreffs"
+  SITEMAP_COLLAPSED_PATHS = %w[updates club/erfas club/chaostreffs disclosure].freeze
 
   NODE_KINDS = {
     "top_level" => {