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/arrlit_slice_assign_named_accept/case.ww

@@ -0,0 +1,9 @@
+//ww:run-exit 1
+package main;
+
+export fn main() i32 = {
+	let a: [3]i32 = [1, 2, 3];
+	let s: []i32 = a[0:1];
+	s = a;
+	return s[0];
+};