build(editor): halkyon_editor joins the workspace (ADR 0033, D37)

The package for the general parts of Learn's editor, its strings first;
the code moves next.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

.dockerignore

@@ -37,6 +37,7 @@ apps/train/halkyon_train_flutter/
 apps/train/halkyon_train_client/
 apps/train/halkyon_train_server/.serverpod/
 packages/halkyon_app/
+packages/halkyon_editor/
 packages/halkyon_interop/
 packages/halkyon_keys/
 packages/halkyon_ui/