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/controls_parts.ludic

@@ -0,0 +1,46 @@
+# controls_parts.ludic - what a control shows besides its own parts: its label, with a `note` (a line
+# of help under it) in .ui-labels > .ui-label + .ui-note, and a range's or a number's value as text:
+# `decimals="1"` places, `format="percent"` its place between min and max, and a `unit` after it
+function ct_label(n: UiNode) -> void {
+  let label = ui_attr_text(n, "label")
+  let note = ui_attr_text(n, "note")
+  if note == "" {
+    if label != "" { push(n.children, ct_part(n, "ui-label", ui_tr(label))) }
+    return
+  }
+  let both = ct_part(n, "ui-labels", "")
+  if label != "" { push(both.children, ct_part(n, "ui-label", ui_tr(label))) }
+  push(both.children, ct_part(n, "ui-note", ui_tr(note)))
+  push(n.children, both)
+}
+function ct_value_text(n: UiNode) -> string {
+  let v = ui_attr(n, "value")
+  if Value.kind(v) == 0 { return "" }
+  var f = Value.as_float(v)
+  let fmt = ui_attr_text(n, "format")
+  if fmt == "percent" {
+    let lo = Value.as_float(ui_attr(n, "min"))
+    var hi = Value.as_float(ui_attr(n, "max"))
+    if hi <= lo { hi = lo + 1.0 }
+    f = (f - lo) / (hi - lo) * 100.0
+  }
+  var s = ""
+  if Value.kind(ui_attr(n, "decimals")) != 0 { s = ct_fixed(f, Value.as_int(ui_attr(n, "decimals"))) } else if fmt == "percent" { s = string(int(Math.round(f))) } else { s = vl_text(v) }
+  if fmt == "percent" { s = s + "%" }
+  return s + ui_attr_text(n, "unit")
+}
+# a number with `places` digits after the point, rounded
+function ct_fixed(f: float, places: int) -> string {
+  var k = 1
+  for i in 0 .. Math.max(places, 0) { k = k * 10 }
+  let neg = f < 0.0
+  let whole = int(Math.round(Math.abs(f) * float(k)))
+  var s = string(whole / k)
+  if places > 0 {
+    var frac = string(whole % k)
+    while len(frac) < places { frac = "0" + frac }
+    s = s + "." + frac
+  }
+  if neg and whole != 0 { s = "-" + s }
+  return s
+}