feat: replace eager list-based map/where with deferred MapSequence and WhereSequence classes

Introduce MapSequence and WhereSequence subclasses of Sequence that apply transformations lazily during iteration instead of building intermediate lists. Update Sequence.map and Sequence.where to return these deferred wrappers, modify all existing tests to call .list on results, and add new infinite-sequence tests verifying lazy behavior on Fibonacci iterators.

src/vm/wren_core.c

@@ -72,21 +72,9 @@ static const char* libSource =
 "    return result\n"
 "  }\n"
 "\n"
-"  map(f) {\n"
-"    var result = new List\n"
-"    for (element in this) {\n"
-"      result.add(f.call(element))\n"
-"    }\n"
-"    return result\n"
-"  }\n"
+"  map(transformation) { new MapSequence(this, transformation) }\n"
 "\n"
-"  where(f) {\n"
-"    var result = new List\n"
-"    for (element in this) {\n"
-"      if (f.call(element)) result.add(element)\n"
-"    }\n"
-"    return result\n"
-"  }\n"
+"  where(predicate) { new WhereSequence(this, predicate) }\n"
 "\n"
 "  all(f) {\n"
 "    for (element in this) {\n"
@@ -146,6 +134,32 @@ static const char* libSource =
 "  }\n"
 "}\n"
 "\n"
+"class MapSequence is Sequence {\n"
+"  new(seq, f) {\n"
+"    _seq = seq\n"
+"    _f = f\n"
+"  }\n"
+"\n"
+"  iterate(n) { _seq.iterate(n) }\n"
+"  iteratorValue(iterator) { _f.call(_seq.iteratorValue(iterator)) }\n"
+"}\n"
+"\n"
+"class WhereSequence is Sequence {\n"
+"  new(seq, f) {\n"
+"    _seq = seq\n"
+"    _f = f\n"
+"  }\n"
+"\n"
+"  iterate(n) {\n"
+"    while (n = _seq.iterate(n)) {\n"
+"      if (_f.call(_seq.iteratorValue(n))) break\n"
+"    }\n"
+"    return n\n"
+"  }\n"
+"\n"
+"  iteratorValue(iterator) { _seq.iteratorValue(iterator) }\n"
+"}\n"
+"\n"
 "class String is Sequence {\n"
 "  bytes { new StringByteSequence(this) }\n"
 "}\n"