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>

packages/halkyon_editor/analysis_options.yaml

@@ -0,0 +1,11 @@
+# The workspace's lint rules (see ../../analysis_options.yaml).
+include: ../../analysis_options.yaml
+
+analyzer:
+  exclude:
+    - build/**
+    # Generated by gen-l10n (see l10n.yaml).
+    - lib/l10n/halkyon_editor_localizations*.dart
+
+formatter:
+  trailing_commas: preserve