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_isbuffered_v_discriminate/case.ww

@@ -0,0 +1,22 @@
+//ww:run-exit 48
+// Migrated from 778_bufio_vstream_run row isbuffered_v_discriminate.
+package main;
+import os;
+import bufio;
+import memio;
+import io;
+export fn main() i32 = {
+    let raw: [8]u8;
+    let mst: memio.stream = memio.fixed(raw[0:8]);
+    let msrc: io.stream = &mst.vt;
+    let rbuf: [4]u8;
+    let wbuf: [4]u8;
+    let b: bufio.stream = bufio.init(msrc, rbuf[0:4], wbuf[0:4]);
+    let vsbuf: io.stream = &b.vt;
+    let buf2: [4]u8;
+    let st2: memio.stream = memio.fixed(buf2[0:4]);
+    let vsplain: io.stream = &st2.vt;
+    if (!bufio.isbuffered(vsbuf)) { return 91; };
+    if (bufio.isbuffered(vsplain)) { return 92; };
+    return 48;
+};