review(#1660, #1663): associative sweep scan, arc angles, viewport off bit

- refresh_associative_sweeps runs on every edit and scanned the xdata of
  every entity; it now returns at once when no associative swept surface
  exists (its application is not registered) and looks at surfaces only.
- An arc's end angle was raised by TAU in a loop, which never ends on a
  huge angle from a damaged file; the sweep is taken with rem_euclid.
- The sweep DELOBJ test expected surface sweeps to delete their sources,
  which #1663 changed on purpose: an associative surface keeps them.
- codec c9ffcac (opencadcodec #103) adds an explicit viewport-off bit: the
  viewport on state is read with is_on() and set with turn_on()/turn_off()
  everywhere, so a viewport the file marks off shows off and can be turned
  back on from Properties.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/scene/modify.rs

@@ -1140,8 +1140,13 @@ impl Scene {
             .filter(|(_, kind)| !matches!(kind, crate::scene::ChangeKind::Removed))
             .map(|(handle, _)| *handle)
             .collect::<rustc_hash::FxHashSet<_>>();
-        if changed.is_empty() { return Vec::new(); }
+        // Every edit passes through here: a drawing with no associative
+        // swept surface (no application registered for them) skips the scan.
+        if changed.is_empty() || !self.document.app_ids.contains(sweep_model::SWEEP_SOURCES_APP) {
+            return Vec::new();
+        }
         let linked = self.document.entities()
+            .filter(|entity| matches!(entity, EntityType::Surface(_)))
             .filter_map(|entity| {
                 let handle = entity.common().handle;
                 let (profile, path) = sweep_model::sweep_sources(entity)?;