Selection: a marquee selects an Intertwine group or a repeat only where it meets their art

A marquee measured an Intertwine group and a repeat by their bounding
box. A marquee in the gap between two members of an Intertwine group,
or between two copies of a repeat, selected the object, although a
click there misses and a plain group needs a marquee to meet one of its
members. Direct and Group Selection's marquees also selected the
Intertwine group whole beside the anchor points of its members.

The marquee now touches an Intertwine group by its members, as it
touches a plain group, and it touches a repeat by the copies the repeat
draws, as clicks hit them. Direct and Group Selection's marquees select
the anchor points of an Intertwine group's members, and Group
Selection's E marquee selects the members inside it. Blends, and
envelopes outside Edit Contents, keep their box, as clicks on them do.

Docs: docs/target-app-parity.md.

docs/target-app-parity.md

@@ -504,6 +504,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
     The Lasso picks anchor points only on art a click can pick, and the Add Anchor Point, Delete Anchor Point, Anchor Point and Scissors tools pick anchor points and segments only on the selected paths and on art a click can pick: not on a Shaper Group's original shapes outside Construction mode, and in isolation mode only inside the isolated group or object. Smart Guides and Snap to Point do not snap to a Shaper Group's original shapes, and the reference point of the transform tools snaps to one only when it is selected, or under the pointer in Construction mode.
     A marquee selects a clip group, or an object on a layer with a clipping mask, only when it reaches the area inside the clipping path, and it measures the art only within that path's bounds. Within the bounds of a mask that is not a rectangle, it can still select art that the mask hides. Direct Selection's marquee still selects the hidden anchor points inside it (#2345).
     A marquee selects a Shaper Group only when it reaches the art the group shows, not the original shapes kept under it, and Direct Selection's clicks and marquee do not select those shapes' anchor points. In Construction mode a marquee selects the original shapes, and Direct Selection selects their anchor points.
+    A marquee selects an Intertwine group only when it reaches one of the group's members, as for a plain group, and it selects a repeat only when it reaches one of the copies the repeat draws. Direct and Group Selection's marquees select the anchor points of an Intertwine group's members, not the group, and Group Selection's E marquee selects the members inside it.
     A key object needs another selected object outside it. A Shift-click or any other change that leaves one object selected clears the key, and `select.key` sets none on one object or on a group selected with only its own members. With one object selected, the Align panel, the Control bar and the Properties panel align it to the artboard whatever Align To is set to.
     With two or more objects selected and no key object, Align to Key Object makes the topmost of them the key, whatever order they were selected in, and the Align panel, the Control bar and the Properties panel align to it. Align To keeps its Selection or Artboard choice and shows it again once the key is cleared.
     Object › Align aligns objects as the align buttons do: it aligns one object to the active artboard whatever Align To is set to, and otherwise it aligns to the key object while there is one, else to the Align To choice, which is saved with the preferences (`ui.inspect` → `ui.align_to`). With direct-selected anchor points, Object › Align aligns the points to their own bounds. While one object is selected, Align To shows Artboard.