feat: add lazy Sequence.skip and Sequence.take methods with SkipSequence and TakeSequence classes

Implement SkipSequence and TakeSequence as lazy iterator-producing wrappers in the core Sequence class. SkipSequence advances past the first count elements on initial iteration, while TakeSequence tracks taken count via _taken field and returns null when exceeded. Include documentation in sequence.markdown, update wren_core.wren.inc, and add test files for both methods covering edge cases (zero, negative, overflow counts).

test/core/sequence/skip.wren

@@ -0,0 +1,28 @@
+class TestSequence is Sequence {
+  construct new() {}
+
+  iterate(iterator) {
+    if (iterator == null) return 1
+    if (iterator == 3) return false
+    return iterator + 1
+  }
+
+  iteratorValue(iterator) { iterator }
+}
+
+var test = TestSequence.new().skip(0)
+
+System.print(test is Sequence) // expect: true
+System.print(test) // expect: instance of SkipSequence
+
+// Skipping 0 changes nothing
+System.print(test.toList) // expect: [1, 2, 3]
+
+// Skipping 1 works
+System.print(test.skip(1).toList) // expect: [2, 3]
+
+// Skipping more than length of sequence produces empty list
+System.print(test.skip(4).isEmpty) // expect: true
+
+// Skipping less than 0 changes nothing
+System.print(test.skip(-10).toList) // expect: [1, 2, 3]

test/core/sequence/take.wren

@@ -0,0 +1,28 @@
+class TestSequence is Sequence {
+  construct new() {}
+
+  iterate(iterator) {
+    if (iterator == null) return 1
+    if (iterator == 3) return false
+    return iterator + 1
+  }
+
+  iteratorValue(iterator) { iterator }
+}
+
+var test = TestSequence.new().take(3)
+
+System.print(test is Sequence) // expect: true
+System.print(test) // expect: instance of TakeSequence
+
+// Taking 0 produces empty list
+System.print(test.take(0).isEmpty) // expect: true
+
+// Taking 1 works
+System.print(test.take(1).toList) // expect: [1]
+
+// Taking more than length of sequence produces whole sequence
+System.print(test.take(4).toList) // expect: [1, 2, 3]
+
+// Taking less than 0 produces empty list
+System.print(test.take(-10).isEmpty) // expect: true