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_stream_write_flush/case.ww

@@ -0,0 +1,29 @@
+//ww:run-exit 46
+// Migrated from 778_bufio_vstream_run row stream_write_flush.
+package main;
+import os;
+import bufio;
+import memio;
+import io;
+export fn main() i32 = {
+    let raw: [16]u8;
+    let mst: memio.stream = memio.fixed(raw[0:16]);
+    let msrc: io.stream = &mst.vt;
+    let rbuf: [8]u8;
+    let wbuf: [8]u8;
+    let b: bufio.stream = bufio.init(msrc, rbuf[0:8], wbuf[0:8]);
+    let vs: io.stream = &b.vt;
+    let payload: [5]u8;
+    payload[0] = 104u8; payload[1] = 105u8;
+    payload[2] = 33u8; payload[3] = 98u8; payload[4] = 121u8;
+    let wr = io.write(vs, payload[0:5]);
+    let nw: size = 0;
+    if (wr is size) { nw = wr as size; };
+    if (mst.pos != 0) { return 91; };
+    let cl = io.close(vs);
+    if (cl is io.error) { return 92; };
+    if (mst.pos != 5) { return 93; };
+    if (nw != 5: size) { return 94; };
+    if (raw[0] != 104u8 || raw[4] != 121u8) { return 95; };
+    return 46;
+};