feat(ui): number and key fields, notes, anchored popovers, text-shadow, and pictures as painted

- <input type="number" min max step>: typed digits replace its value (a minus when min allows one,
  a point when step has a fraction), Enter or leaving the field commits them held between min and
  max, the left and right arrows step it.
- <input type="key">: Enter or a click starts it listening and the next key is its value, Tab, the
  arrows and Enter included; Esc stops it listening, Backspace clears it, `shown` names the value,
  and ui_capturing() tells the host to leave its keys alone (through the frame that ended it).
- note="..." under any control's label (.ui-labels > .ui-label + .ui-note); a range's (or number's)
  value with decimals, format="percent" and a unit.
- A popover with `anchor="id"` (the nearest element of that id) or a bare `anchor` (the element
  before it) sits beside it by `placement` (right, left, bottom, top), its margin the gap, opens to
  the other side where it would leave the screen, and is kept on it.
- A tooltip's title splits into lines at a newline or a written \n.
- text-shadow, inherited, drawn sharp under the text.
- ui_opacity(): the group opacity a native's draw is at.
- border-image is drawn as painted with no background colour, tinted by one, and not at all when
  that colour is transparent (it drew a white nine-slice).
- A picture file is drawn untinted, as a browser draws one; an atlas cell (prefix:name) still takes
  the color around it, and an <img> with its own color is tinted by it.
- The render3d backend loads a picture again when its file changes or appears (a failed load was
  kept for ever), and at once after ui_image_reload(path); takes a path with a drive letter (C:/...)
  as a path rather than an atlas; and slices a nine-slice by its texture's own width and height.
- ui_inputs.ludic and ui_look.ludic; LANGUAGE.md and the changeset say all of it.

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

packages/ludic.ui/render3d_nine.ludic

@@ -0,0 +1,29 @@
+# render3d_nine.ludic - border-image for the render3d backend: a nine-slice of a texture
+module ludic_ui
+# border-image: the texture's `slice`-pixel corners kept, the rest stretched, drawn `dst` wide; the
+# slice is a share of the texture's own width across and its own height down, so it need not be square
+function r3u_nine(src: string, slice: float, x: float, y: float, w: float, h: float, dst: float, c: int, a: float) -> void {
+  let t = r3u_tex(src)
+  if t == 0 { return }
+  let su = slice / float(Math.max(tex_width(t), 1))
+  let sv = slice / float(Math.max(tex_height(t), 1))
+  let xs = r3u_four(x, x + dst, x + w - dst, x + w)
+  let ys = r3u_four(y, y + dst, y + h - dst, y + h)
+  let us = r3u_four(0.0, su, 1.0 - su, 1.0)
+  let vs = r3u_four(0.0, sv, 1.0 - sv, 1.0)
+  for j in 0 .. 3 {
+    for i in 0 .. 3 {
+      let x0 = int(xs[i])
+      let y0 = int(ys[j])
+      ov_sub(t, x0, y0, int(xs[i + 1]) - x0, int(ys[j + 1]) - y0, us[i], vs[j], us[i + 1], vs[j + 1], r3u_r(c), r3u_g(c), r3u_b(c), a)
+    }
+  }
+}
+function r3u_four(a: float, b: float, c: float, d: float) -> []float {
+  let out = new []float
+  push(out, a)
+  push(out, b)
+  push(out, c)
+  push(out, d)
+  return out
+}