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/r773_same_module_variant/case.ww

@@ -0,0 +1,9 @@
+//ww:run-exit 3
+// Migrated from 773_isas_spread_variant row same_module_variant.
+package main;
+export fn main() i32 = {
+    let r: (i32 | str) = 3: i32;
+    if (r is i32) { return 3; };
+    if (r is str) { return 1; };
+    return 0;
+};