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/r660_chained_i16_leaf/case.ww

@@ -0,0 +1,5 @@
+//ww:run-exit 42
+package main;
+type inner = struct { v: i16, pad: i16 };
+type outer = struct { i: inner, tag: i32 };
+fn main() i32 = { let o: outer; o.i.v = -32768i64: i16; o.i.pad = 0i16; o.tag = 0; let z: i64 = o.i.v: i64; if (z == -32768i64) { return 42; }; return 0; };