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>

runtime/native/namespaces.ludic

@@ -462,6 +462,7 @@ namespace Value {
   alias null() = value_null
   alias int(n) = value_int
   alias fixed(f) = value_fixed
+  alias float(x) = value_float
   alias bool(b) = value_bool
   alias str(s) = value_str
   alias list() = value_list
@@ -475,6 +476,7 @@ namespace Value {
   alias count(value) = value_count
   alias kind(value) = value_kind
   alias as_int(value) = value_as_int
+  alias as_float(value) = value_as_float
   alias as_str(value) = value_as_str
 }
 namespace Json {