ww: driver/coordinator robustness — dirent errors, EINTR, block comments

Three same-cluster robustness holes. enumeratedir treated a failed
getdents64 (r<0) as EOF: a mid-walk error silently truncated the
package source list, and a first-read error was misdiagnosed as
"directory contains no WW package sources" -- it now routes the
caller's "cannot read directory" arm. run_test_bin's waitpid had no
EINTR retry and its return was unchecked, so an interrupted wait
left status==0 and reported a false test PASS (the do_run twin
already retried). The coordinator's pkgskipspace now also skips
/* */ before the package clause like the driver's sep_skip_space --
a source opening with a block comment built under ww but failed
coordinator discovery.

selfhost/cmd/ww/main.ww

@@ -469,6 +469,14 @@ fn enumeratedir(dirpath: *u8) (**u8, i32) = {
 		r = os.getdents64(fd, buf.ptr, 8192u64);
 	};
 	os.close(fd);
+	// A failed directory read is an ERROR, not EOF: mid-walk it
+	// silently truncated the package source list, and on the first
+	// read it was misdiagnosed as "directory contains no WW package
+	// sources". -1 routes the caller's "cannot read directory" arm
+	// (the cstage caller mapping).
+	if (r < 0i64) {
+		return nil: **u8, -1;
+	};
 
 	// Insertion sort, byte-wise. n is small (≤16 in practice).
 	let i: i32 = 1;