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/index.ludic

@@ -1,8 +1,10 @@
 # ludic.ui - templates: screens and components written as markup in files the program loads at
 # run time, reading only what a `view` declaration lets them, and answering with its events
-module ui
+module ludic_ui
 numbers float
+import "consts.ludic"
 import "node.ludic"
+import "view.ludic"
 import "backend.ludic"
 import "expr.ludic"
 import "expr_parse.ludic"
@@ -15,13 +17,17 @@ import "native.ludic"
 import "forms.ludic"
 import "life.ludic"
 import "tpl.ludic"
+import "tpl_lines.ludic"
 import "lib.ludic"
 import "lib_util.ludic"
+import "class.ludic"
+import "instance.ludic"
 import "reload.ludic"
 import "link.ludic"
 import "state.ludic"
 import "build.ludic"
 import "build_more.ludic"
+import "build_class.ludic"
 import "elem.ludic"
 import "attr.ludic"
 import "attr_box.ludic"
@@ -39,5 +45,7 @@ import "layout_text.ludic"
 import "layout_run.ludic"
 import "layout_wrap.ludic"
 import "frame.ludic"
+import "pointer.ludic"
+import "screen_class.ludic"
 import "draw.ludic"
 import "dump.ludic"