fix(copy): a copy reacts only to what was copied with it

COPY and PASTE kept the source's reactors on each copy, so a copied
dimension still pointed at the source's dimension association (and
boundary or group members at the source hatch or group). Another
application reports such a drawing as damaged and, after recovery,
moves the dimensions. A copy's reactors now follow only targets copied
with it; group copies give their members the new group's reactor; and a
drawing opened with such stray dimension reactors has them dropped.

Fixes #1645
Fixes #1649

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

src/app/command_driver/clipboard.rs

@@ -578,6 +578,8 @@ pub(crate) fn paste_entities_kernel(
     // A pasted associative hatch follows the pasted boundary, or drops the
     // association when the boundary was not pasted with it. (#1370)
     crate::scene::remap_hatch_associations(doc, &handle_map);
+    // Reactors on the source drawing's objects do not travel with the paste.
+    crate::scene::remap_copied_reactors(doc, &handle_map);
     let leader_links: Vec<(Handle, Handle)> = entities
         .iter()
         .filter_map(|source| {