Halkyon's shared packages

A pub workspace of the Dart packages Halkyon's apps share: halkyon_ui,
Halkyon's look (the theme, fonts, layout and shared widgets, with texts
in English and German), halkyon_core's low-level primitives and
halkyon_interop's cross-app contracts. Dart 3.13 with LeanCode's lints,
configured once at the root; apps take a package by git, pinned to a
signed commit.

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

README.md

@@ -0,0 +1,18 @@
+# halkyon_shared
+
+Shared Dart packages across Halkyon apps, a pub workspace:
+
+- [`halkyon_ui`](packages/halkyon_ui): Halkyon's look, the theme, fonts, layout
+  and shared widgets (Flutter).
+- [`halkyon_core`](packages/halkyon_core): low-level primitives (pure Dart).
+- [`halkyon_interop`](packages/halkyon_interop): cross-app contracts (pure Dart).
+
+Dart 3.13 and Flutter 3.47, with LeanCode's lints (`leancode_lint`), configured
+once in `analysis_options.yaml` here, which every package includes: its
+analyzer plugin only reaches packages of a workspace from the root. Run
+`flutter pub get` and `dart analyze --fatal-infos` here, and each package's
+tests in its folder (`dart test`, or `flutter test` for `halkyon_ui` and its
+example).
+
+Apps take a package by git, pinned to a signed commit; see
+[`halkyon_ui`'s README](packages/halkyon_ui/README.md).