feat(help): open a generated command reference instead of Discussions (#1049)

HELP now opens docs/command-reference.md on GitHub — a 600-command
reference grouped by category with default shortcuts and selection
behavior, generated from the in-repo command registry. A staleness
test fails when the registry and the page drift apart; regenerate
with UPDATE_COMMAND_REFERENCE=1 cargo test command_reference. The
command-line notice is localized in all 21 languages.

locales/fr-FR/opencadstudio.ftl

@@ -3563,6 +3563,7 @@ view =
     .objectscale-the-active-annotation-scale-is-una = OBJECTSCALE : l'échelle d'annotation active n'est pas disponible.
     .opening-ocs-discussions-for-help-and-questions = Ouverture OCS Discussions pour l'aide et les questions...
     .opening-ocs-web = Ouverture du site Web OCS...
+    .opening-the-command-reference = Ouverture de la référence des commandes...
     .opening-patreon-page = Ouverture de la page Patreon...
     .opening-feedback-page = Ouverture de la page de rétroaction...
     .opening-release-notes = Ouverture des notes de sortie...