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/r776_branched_fixed/case.ww

@@ -0,0 +1,26 @@
+//ww:run-exit 45
+// Migrated from 776_memio_vstream_run row branched_fixed.
+package main;
+import memio;
+import io;
+import os;
+export fn main() i32 = {
+    let a: [3]u8;
+    a[0] = 10u8; a[1] = 11u8; a[2] = 12u8;
+    let b: [5]u8;
+    b[0] = 20u8; b[1] = 21u8; b[2] = 22u8; b[3] = 23u8; b[4] = 24u8;
+    let sta: memio.stream = memio.fixed(a[0:3]);
+    let stb: memio.stream = memio.fixed(b[0:5]);
+    let sa: io.stream = &sta.vt;
+    let sb: io.stream = &stb.vt;
+    let outa: [3]u8;
+    let outb: [5]u8;
+    let rda = io.read(sa, outa[0:3]);
+    let rdb = io.read(sb, outb[0:5]);
+    let na: size = 0;
+    let nb: size = 0;
+    if (rda is size) { na = rda as size; };
+    if (rdb is size) { nb = rdb as size; };
+    if (na == 3: size && nb == 5: size && outa[2] == 12u8 && outb[4] == 24u8) { return 45; };
+    return 99;
+};