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/tpl_lines.ludic

@@ -0,0 +1,19 @@
+# tpl_lines.ludic - which line of its file an element is on
+# the text being read, and where its lines start, so an element can say which line it is on
+var tp_nl: []int = new []int
+function tp_lines(src: string) -> void {
+  tp_nl = new []int
+  for i in 0 .. len(src) {
+    if src[i] == 10 { push(tp_nl, i) }
+  }
+}
+function tp_line(at: int) -> int {
+  var lo = 0
+  var hi = len(tp_nl)
+  while lo < hi {
+    let mid = (lo + hi) / 2
+    if tp_nl[mid] < at { lo = mid + 1 } else { hi = mid }
+  }
+  return lo + 1
+}
+