feat(lang): UI components as files - component Name { ... } beside Name.xml and Name.lss

The compiler turns a component declaration into:
- a record of its props and state;
- a constructor, a props setter, a model and a call;
- a class, registered with ludic.ui at start.

Its template and styles are read from beside it and compiled in, with @import inlined, and a
missing template fails the build.

In the runtime:
- each mounted instance keeps its own props and state, and `set` in a template writes the state;
- styles are scoped to the component;
- class, style and id on a component's tag land on its root, styled by the parent's sheet too;
- ui_reload re-reads a component's files from disk and keeps instances.

The package's own module is now ludic_ui, so a program may call a directory of its own ui.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/ludic.ui/view.ludic

@@ -0,0 +1,8 @@
+# view.ludic - a `view` declaration's bridge, for a screen written as a template file of its own
+# what a program lets its templates see: `view Name { ... }` writes view_name() -> UiView
+export property UiView {
+  name: string = ""
+  model: fn() -> Val = null
+  call: fn(string, Val) -> Val = null
+}
+