Retire davewiner's 922 rows, without taking the ones people still read

davewiner's OPML left config.toml before retire_group existed, so its
derived rows were skipped by every scan but never cleared. At startup the
daemon now retires every group whose parent is gone from config. And
retire_group unmanages a feed that has its own config entry instead of
dropping it: eleven of davewiner's were promoted without being unmanaged,
and dropping them as derived would have deleted their entries. That also
covers removing an OPML or Patreon subscription from the page.

Closes #3.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -27,6 +27,11 @@ The long form, with what was wrong before and how it was found, is in
 
 ### Fixed
 
+- The feeds left behind by an OPML subscription removed before ipx retired them are cleared at
+  startup: forgotten if nothing was downloaded, kept as orphaned if something was. Feeds from it
+  that have since been given their own settings stay as they are, with their items. Removing an
+  OPML or Patreon subscription no longer deletes the items of a feed inside it that has its own
+  settings.
 - Titles that arrive as HTML, such as The Verge's, no longer show their entities as text:
   "Meta’s" reads "Meta’s". Titles already stored are corrected the next time their feed
   changes.