planet: disable dead lthms feed (soap.coffee)

The lthms feed (soap.coffee) no longer resolves — the domain has no DNS
record and the scrape fails every day with a name-resolution error (see
#3753). Following the dinosaure/ocaml-book/emilpriver convention, it is
disabled rather than removed so the 21 already-archived posts keep
rendering (they resolve via the source entry, so removing it would fail
the data-packer build).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: cuihtlauac

data/planet-sources.yml

@@ -232,9 +232,12 @@
   name: Dmitrii Kovanikov
   url: https://chshersh.com/atom.xml
   publish_all: false
+# Feed is dead (soap.coffee no longer resolves, see #3753); disabled so it is
+# no longer scraped, but the already-archived posts are kept.
 - id: lthms
   name: "Thomas Letan’s Blog"
   url: https://soap.coffee/~lthms/tags/ocaml.xml
+  disabled: true
 - id: debajyatidey
   name: Debajyati's Blog
   url: https://debajyatidey.hashnode.dev/rss.xml