feat: add logical OR operator with short-circuit evaluation and token support

Add TOKEN_PIPEPIPE token for '||' syntax, implement or() parsing function with CODE_OR bytecode, and add VM interpreter logic that short-circuits on truthy left operand. Update .gitignore to exclude *.xccheckout files, extend test coverage for falsy behavior in and.wren and if.wren, and add comprehensive or.wren test suite verifying short-circuit semantics and truthiness rules.

test/or.wren

@@ -0,0 +1,26 @@
+// Note: These tests implicitly depend on ints being truthy.
+//       Also rely on io.write() returning its argument.
+
+// Return the first true argument.
+io.write(1 || true) // expect: 1
+io.write(false || 1) // expect: 1
+io.write(false || false || true) // expect: true
+
+// Return the last argument if all are false.
+io.write(false || false) // expect: false
+io.write(false || false || false) // expect: false
+
+// Short-circuit at the first true argument.
+io.write(false) || // expect: false
+    io.write(true) || // expect: true
+    io.write(true) // should not print
+
+// Swallow a trailing newline.
+io.write(true ||
+    true) // expect: true
+
+// Only false is falsy.
+io.write(0 || true) // expect: 0
+io.write(null || true) // expect: null
+io.write(("" || true) == "") // expect: true
+io.write(false || true) // expect: true