test/wcc/data: grow the declarative compiler corpus to 1,224 fixtures

The r-prefixed waves absorb the runtime, reject, and byte-compare rows
of the migrated native carriers; each fixture is one directory with one
case.ww and a //ww:error, //ww:compile, //ww:run, or //ww:run-exit
directive covering both frontends.

test/wcc/data/r681_str_field_value_write_regression/case.ww

@@ -0,0 +1,7 @@
+//ww:run-exit 42
+package main;
+type bs = struct { s: str, mark: i32 };
+fn main() i32 = {
+	let b: bs; b.mark = 11; b.s = "hello";
+	if (b.s.len != 5) { return 1; }; if (b.mark != 11) { return 2; }; return 42;
+};