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/r778_branched_bufio_wrap/case.ww

@@ -0,0 +1,29 @@
+//ww:run-exit 51
+// Migrated from 778_bufio_vstream_run row branched_bufio_wrap.
+package main;
+import os;
+import bufio;
+import memio;
+import io;
+export fn main() i32 = {
+    let raA: [4]u8;
+    raA[0] = 10u8; raA[1] = 11u8; raA[2] = 12u8; raA[3] = 13u8;
+    let raB: [4]u8;
+    raB[0] = 20u8; raB[1] = 21u8; raB[2] = 22u8; raB[3] = 23u8;
+    let mstA: memio.stream = memio.fixed(raA[0:4]);
+    let mstB: memio.stream = memio.fixed(raB[0:4]);
+    let sel: i32 = 1;
+    let src: io.stream = &mstA.vt;
+    if (sel == 0) { src = &mstB.vt; };
+    let rbuf: [4]u8;
+    let wbuf: [4]u8;
+    let bc: bufio.stream = bufio.init(src, rbuf[0:4], wbuf[0:4]);
+    let vs: io.stream = &bc.vt;
+    let out: [4]u8;
+    let rd = io.read(vs, out[0:4]);
+    let n: size = 0;
+    if (rd is size) { n = rd as size; };
+    if (n != 4: size) { return 91; };
+    if (out[0] != 10u8 || out[3] != 13u8) { return 92; };
+    return 51;
+};