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/r744_letcopy_str/case.ww

@@ -0,0 +1,13 @@
+//ww:run
+package main;
+import os;
+type ws = struct { a: i32, s: str };
+fn produce() i32 = {
+	let p1: ws;
+	p1.a = 7; p1.s = "hi";
+	let p2: ws = p1;
+	if (p2.a != 7) { return 11; };
+	if (p2.s.len != 2) { return 12; };
+	return 0;
+};
+export fn main() i32 = { os.exit(produce()); };