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/r76_infer_struct_i64_i32_tail/case.ww

@@ -0,0 +1,6 @@
+//ww:run-exit 57
+package main;
+type ntail = struct { a: i64, b: i32 };
+fn make(flag: i32) ntail = { if (flag == 0) { return ntail { a = 50i64, b = 7i32 }; }; return ntail { a = 500i64, b = 70i32 }; };
+fn use_(p: ntail, which: i32) i32 = { if (which == 0) { return (p.a + (p.b: i64)): i32; }; return (p.a - (p.b: i64)): i32; };
+fn main() i32 = { let p = make(0); return use_(p, 0); };