feat(ui): flex-shrink, text that wraps beside its siblings, calc(), order, and 0 as a size

- flex-shrink: a line whose children want more room than it has takes it back from those that
  shrink, in proportion to shrink times size and never below a min size, a fixed size or the
  content. A scroll box shrinks (and scrolls), and a box in a column shrinks as far as the scroll
  boxes inside it let it, so a list in a column takes the room its siblings leave with no height.
  `flex: grow shrink`, and `flex-shrink` by name.
- A row wider than its room measures its texts (and boxes without a width) again in the room the
  rest leave them, so a line wraps beside an icon.
- calc() with + - * / and brackets over px, %, em, rem, vw, vh, plain numbers and var(); a width
  or height keeps its percentage, taken of the room it is given. Lengths lists (padding, margin)
  keep a calc()'s spaces.
- `order` places a box's children without touching the tree.
- width: 0 and height: 0 are 0: an unset size is UI_AUTO now, not 0.
- A component root that is itself a component takes each user's class, style and id in turn (the
  outermost's id wins), and the rules of all their sheets are weighed by specificity together; a
  user's rule wins a tie. The parent's sheet used to override the child's whatever its specificity,
  and a middle component's sheet was lost.
- The default sheet lays .ui-track out as a row, so a range's fill is as tall as its track and a
  checked box's knob goes right; a range's thumb is centred on the fill's end.
- ui_boxes.ludic.

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

packages/ludic.ui/node.ludic

@@ -12,15 +12,13 @@ export property UiNode {
   vals: []Val = null            # the same, as values, applied after every rule
   style: UiRule = null          # its style="..." declarations
   sheet: UiSheet = null         # the stylesheets of the file it was written in
-  sheet2: UiSheet = null        # a component's root: its user's sheet too, and their style="..."
-  style2: UiRule = null
-  env2: UiEnv = null
+  ups: []UiPass = null          # a component's root: each user's sheet and style="...", inner first
   parent: UiNode = null
   index: int = 0                # its place among its parent's children, for :first-child and the rest
   src: string = ""              # an <img>'s picture
   size: float = 0.0
-  w: float = 0.0
-  h: float = 0.0
+  w: float = -1000000.0         # a fixed width or height (0 is 0); UI_AUTO: none, UI_FILL: fill
+  h: float = -1000000.0
   w_pct: float = 0.0            # a width or height as a percentage of the parent's room
   h_pct: float = 0.0
   pt: float = 0.0               # padding, top right bottom left
@@ -108,5 +106,6 @@ export property UiNode {
   anim_alt: bool = false
   tr_dur: float = 0.0           # transition: how long a change of opacity takes
   popover: bool = false         # drawn on the top layer; a press outside it or Esc closes it
+  ex: UiNodeX = null            # what fewer elements say (node_more.ludic), made when one does
 }