fix(sheet): keep a stored fold working when its fixed point drifts off the sheet (#370) (#537)

A stored fold whose fixed point drifts off the sheet after a parameter change keeps the side the point lies on and shows a warning instead of breaking the timeline. A new fold still refuses a fixed point off the sheet, atomically. Un-ignores the #370 regression test. Fixes #370.

Co-authored-by: jonaswre <jonas.wrede@beyondit.gmbh>

crates/doc/src/eval_more.rs

@@ -505,7 +505,7 @@ pub(super) fn sheet_eval(
                 return Err(DocError::Invalid("refold the sheet before folding it".into()));
             }
             let n0 = sh.flanges.len();
-            sh.add_fold(a, b, ang, rr, position, *flip, *fixed)?;
+            sh.add_fold(a, b, ang, rr, position, *flip, *fixed, warning)?;
             tag_flanges(sh, n0, f.id);
             rebuild_sheet(st, i)
         }