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/r707_mixed_variants_in_loop/case.ww

@@ -0,0 +1,23 @@
+//ww:run-exit 0
+package main;
+type ft = (i64 | str | bool);
+fn askstr(s: str) ft = { return s; };
+fn aski64(v: i64) ft = { return v; };
+fn main() i32 = {
+    let arr: [2]i64 = [10i64, 20i64];
+    let i: i32 = 0;
+    let bad: i32 = 0;
+    for (i < 2) {
+        let _v: i64 = arr[i];
+        let a: ft;
+        let expect: i64 = 0i64;
+        if (i == 0) { a = askstr("world"); expect = 5i64; };
+        if (i == 1) { a = aski64(99i64);    expect = 0i64; };
+        let p: u64 = (&a): u64;
+        let p2: *i64 = (p + 16u64): *i64;
+        let w: i64 = *p2;
+        if (w != expect) { bad += 1; };
+        i += 1;
+    };
+    return bad;
+};