Replace awesome_nested_set with a plain parent_id-based NestedTree concern

Root-caused this session: appending a child to any node never widened
that parent's own rgt boundary, on the pinned revision (Gemfile tracked
main directly, chasing a too-conservative gemspec constraint - not, as
first assumed, a deliberate pin to avoid a known bug). Reproduced
cleanly on a single ordinary create with no concurrency and no bulk
operation involved, confirmed via the gem's own SetValidator, then
confirmed as the root cause of nodes_controller_test.rb's 3 long-standing
"pre-existing" failures - not three separate mysteries, one bug.

admin_controller's sitemap needed its own real conversion, not just a
drop-in: awesome_nested_set's lft column implicitly provided correct
depth-first tree order for free, which the old code combined with a
separate class-level each_with_level iterator. Both replaced by one
method, self_and_descendants_ordered_with_level, computing an ordered
[node, level] list in a single query-then-walk pass - checked against
the actual view template first (admin/index.html.erb) rather than
assumed, since it relies on list order alone to render correct visual
nesting.

lft/rgt/depth columns intentionally left in schema, unused - dropping
them is a separate, deliberately deferred migration once this is proven
running for a while, not bundled with the behavior change.

1 files changed, 0 insertions, 10 deletions

diff --git a/Gemfile.lock b/Gemfile.lock
index 2e9a1ce..02c71ff 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,12 +1,4 @@
 GIT
-  remote: https://github.com/collectiveidea/awesome_nested_set.git
-  revision: 7a642749af74519b4bf3642d939061beb36835e1
-  branch: main
-  specs:
-    awesome_nested_set (3.9.0)
-      activerecord (>= 4.0.0, < 8.2)
-
-GIT
   remote: https://github.com/erdgeist/chaoscalendar.git
   revision: 48fe5c517ae3895cc78d9d2fefbdd35b90d52ba7
   branch: erdgeist-ruby1.9
@@ -335,7 +327,6 @@ PLATFORMS
 DEPENDENCIES
   acts-as-taggable-on!
   acts_as_list
-  awesome_nested_set!
   chaos_calendar!
   coffee-rails (~> 4.0)
   concurrent-ruby (~> 1.3)
@@ -374,7 +365,6 @@ CHECKSUMS
   activesupport (8.1.3) sha256=21a5e0dfbd4c3ddd9e1317ec6a4d782fa226e7867dc70b0743acda81a1dca20e
   acts-as-taggable-on (13.0.0)
   acts_as_list (1.2.6) sha256=8345380900b7bee620c07ad00991ccee59af3d8c9e8574f426e321da2865fdc8
-  awesome_nested_set (3.9.0)
   base64 (0.3.0) sha256=27337aeabad6ffae05c265c450490628ef3ebd4b67be58257393227588f5a97b
   bigdecimal (4.1.2) sha256=53d217666027eab4280346fba98e7d5b66baaae1b9c3c1c0ffe89d48188a3fbd
   builder (3.3.0) sha256=497918d2f9dca528fdca4b88d84e4ef4387256d984b8154e9d5d3fe5a9c8835f