feat(lang): L11 views and templates - the UI is markup, not code

A `view Name { field = x; function q(..); on e(..) }` declaration is the one bridge between a
program and its UI: it writes view_<name>() -> UiView, whose model is a Value of every field and
whose call runs a query or an event by name.

ludic.ui is a template runtime:
- HTML-shaped XML screens and components, loaded at run time;
- {expression} bindings, if/else/each, props, slots, per-instance state;
- on-press / onclick actions (event, set, emit);
- component libraries (export="true", <import src as>).

Styling:
- stylesheets in <style> or importable .lss files (@import);
- CSS selectors (#id, .class, [attr=v], descendant and > combinators, :hover, :disabled,
  :first-child, :last-child, :nth-child, :not) weighed by specificity;
- the box model and flex under CSS's property names.

Also:
- default parameters, and positional-then-named calls;
- Value gains a float kind;
- a function shadowing a runtime one is refused;
- an index is evaluated before the slice is read;
- runtime errors name the right file.

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

packages/ludic.ui/index.ludic

@@ -0,0 +1,33 @@
+# 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
+numbers float
+import "node.ludic"
+import "backend.ludic"
+import "expr.ludic"
+import "expr_parse.ludic"
+import "expr_prim.ludic"
+import "values.ludic"
+import "env.ludic"
+import "eval.ludic"
+import "act.ludic"
+import "tpl.ludic"
+import "lib.ludic"
+import "lib_util.ludic"
+import "link.ludic"
+import "state.ludic"
+import "build.ludic"
+import "elem.ludic"
+import "attr.ludic"
+import "attr_box.ludic"
+import "style.ludic"
+import "style_rule.ludic"
+import "select.ludic"
+import "select_parts.ludic"
+import "select_match.ludic"
+import "cascade.ludic"
+import "layout.ludic"
+import "layout_run.ludic"
+import "layout_wrap.ludic"
+import "frame.ludic"
+import "draw.ludic"