feat(ui): ludic.ui grows toward HTML, CSS and React (Phase 0.U1-U4)

- Natives: ui_native(tag, measure, draw) makes an element the program draws itself; ui_fire
  runs its on-<event> with event.value. input, select and textarea have simple defaults.
- React:
  - keyed <each>, <let>, <provide> context through components, <fragment>;
  - named slots, default props on <component>;
  - on-mount / on-unmount;
  - inline text inside text elements.
- CSS:
  - custom properties and var();
  - position relative/absolute/fixed with insets and z-index;
  - em/rem/vw/vh and @media;
  - wrapping text and ellipsis, overflow;
  - + and ~ combinators, :nth-child(an+b), :checked, :active.
- Developing: errors with file:line, ui_errors(), ui_reload() keeping state, and an
  inspector-style ui_dump.
- view fields infer the type of a literal or a named function's result.

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

packages/ludic.ui/dump.ludic

@@ -0,0 +1,36 @@
+# dump.ludic - a laid-out tree, for a test or a look
+# every node and where it went, one line each - for a test, or a look at a layout
+export function ui_dump(n: UiNode, depth: int) -> string {
+  var pad = ""
+  for d in 0 .. depth { pad = pad + "  " }
+  var out = `{pad}{dp_name(n)} {int(n.x)},{int(n.y)} {int(n.cw)}x{int(n.ch)}{dp_style(n)} {n.text}\n`
+  if n.children != null {
+    for i in 0 .. len(n.children) { out = out + ui_dump(n.children[i], depth + 1) }
+  }
+  return out
+}
+# tag#id.class.class, or the kind of a node the template did not name
+function dp_name(n: UiNode) -> string {
+  var s = n.tag
+  if s == "" { s = `({n.kind})` }
+  if n.id != "" { s = s + "#" + n.id }
+  if n.classes != null {
+    for i in 0 .. len(n.classes) { s = s + "." + n.classes[i] }
+  }
+  return s
+}
+# the computed styles that differ from an element's defaults
+function dp_style(n: UiNode) -> string {
+  var s = ""
+  if n.size > 0.0 { s = s + ` font {int(n.size)}` }
+  if n.fg >= 0 { s = s + ` color {n.fg}` }
+  if n.bg >= 0 { s = s + ` bg {n.bg}` }
+  if n.alpha < 1.0 { s = s + ` opacity {n.alpha}` }
+  if n.pt + n.pr + n.pb + n.pl > 0.0 { s = s + ` pad {int(n.pt)} {int(n.pr)} {int(n.pb)} {int(n.pl)}` }
+  if n.mt + n.mr + n.mb + n.ml > 0.0 { s = s + ` margin {int(n.mt)} {int(n.mr)} {int(n.mb)} {int(n.ml)}` }
+  if n.grow > 0.0 { s = s + ` grow {n.grow}` }
+  if n.pos > 0 { s = s + ` pos {n.pos} z {n.z}` }
+  if not n.enabled { s = s + " disabled" }
+  if s == "" { return "" }
+  return " [" + s[1..len(s)] + "]"
+}