fix(io): keep the clamp rail when its saved removal time is invalid

A negative removalMinutes in a saved nest made the ClampRail constructor
throw, so the reader dropped the whole rail and every sheet lost its
removed-clamp state and time. An invalid value now falls back to the
default five minutes, like a missing one.

PM 6ded8ac4-84fd-4e8b-9a3b-6f41e494542c item (b)

OpenNest.IO.Tests/ClampRailPersistenceTests.cs

@@ -286,6 +286,29 @@ public class ClampRailPersistenceTests
         Assert.Equal(keepsRemoval, plate.ClampRail != null);
     }
 
+    // PM 6ded8ac4 (b): an invalid removal time falls back to the default instead of
+    // dropping the rail and every sheet's removal state with it.
+    [Theory]
+    [InlineData("-1")]
+    [InlineData("\"x\"")]
+    public void InvalidRemovalMinutesFallBackToTheDefault(string minutes)
+    {
+        var tampered = RewriteNestJson(RemovedClamp3Nest(), text =>
+        {
+            var root = JsonNode.Parse(text)!;
+            root["plateDefaults"]!["clampRail"]!["removalMinutes"] = JsonNode.Parse(minutes);
+            return root.ToJsonString();
+        });
+
+        var reopened = new NestReader(tampered).Read();
+
+        Assert.NotNull(reopened.PlateDefaults.ClampRail);
+        Assert.Equal(ClampRail.DefaultRemovalMinutes, reopened.PlateDefaults.ClampRail.RemovalMinutes);
+        var plate = Assert.Single(reopened.Plates);
+        Assert.Equal(new[] { "clamp-3" }, plate.RemovedClamps);
+        Assert.NotNull(plate.ClampRail);
+    }
+
     /// <summary>Removes a named property wherever it appears in the document, simulating a
     /// key an older writer never emitted. Rebuilds via <see cref="JsonNode"/> so the result
     /// is always valid JSON regardless of whether the property was first, last or only one

OpenNest.IO/NestReader.cs

@@ -330,7 +330,7 @@ namespace OpenNest.IO
         /// <summary>
         /// The saved machine clamp rail, or null when absent, empty or malformed (a bad rail
         /// is ignored rather than failing the nest; each plate's saved zones still load). A
-        /// missing removal-minutes value falls back to <see cref="ClampRail.DefaultRemovalMinutes"/>.
+        /// missing or invalid removal-minutes value falls back to <see cref="ClampRail.DefaultRemovalMinutes"/>.
         /// </summary>
         private static ClampRail ReadClampRail(ClampRailDto dto)
         {
@@ -338,12 +338,13 @@ namespace OpenNest.IO
                 return null;
             try
             {
-                return new ClampRail(
-                    dto.Width,
-                    dto.Depth,
-                    dto.Centers,
-                    dto.RemovalMinutes ?? ClampRail.DefaultRemovalMinutes
-                );
+                // An invalid removal time (negative or not finite) falls back to the default
+                // rather than dropping the rail, which would also discard every sheet's
+                // removed-clamp state.
+                var minutes = dto.RemovalMinutes is double m && double.IsFinite(m) && m >= 0
+                    ? m
+                    : ClampRail.DefaultRemovalMinutes;
+                return new ClampRail(dto.Width, dto.Depth, dto.Centers, minutes);
             }
             catch (ArgumentException)
             {