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/media.ludic

@@ -0,0 +1,36 @@
+# media.ludic - @media (min-width: 1280px) and (max-height: 720px) { ... }: rules that hold only
+# while the screen's area is that size
+export property UiMedia {
+  min_w: float = 0.0
+  max_w: float = 0.0
+  min_h: float = 0.0
+  max_h: float = 0.0
+}
+function md_parse(cond: string) -> UiMedia {
+  let m = new UiMedia
+  let parts = lss_split(cond, 40)
+  for i in 0 .. len(parts) {
+    let p = parts[i]
+    var colon = -1
+    for k in 0 .. len(p) {
+      if colon < 0 and p[k] == 58 { colon = k }
+    }
+    if colon < 0 { continue }
+    let key = tpl_words(p[0..colon])
+    let v = el_num(tpl_words(p[colon + 1..len(p)]))
+    if key == "min-width" { m.min_w = v }
+    if key == "max-width" { m.max_w = v }
+    if key == "min-height" { m.min_h = v }
+    if key == "max-height" { m.max_h = v }
+  }
+  return m
+}
+function md_ok(r: UiRule) -> bool {
+  let m = r.md
+  if m == null { return true }
+  if m.min_w > 0.0 and ly_vp_w < m.min_w { return false }
+  if m.max_w > 0.0 and ly_vp_w > m.max_w { return false }
+  if m.min_h > 0.0 and ly_vp_h < m.min_h { return false }
+  if m.max_h > 0.0 and ly_vp_h > m.max_h { return false }
+  return true
+}