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.

internal/wwpackage/package.ww

@@ -164,6 +164,22 @@ fn pkgskipspace(src: str, start: i32) i32 = {
 			for (i < src.len && src[i] != '\n') { i += 1; };
 			continue;
 		};
+		// The driver's sep_skip_space (cmd/ww/main.c) also skips
+		// /* */ before the package clause; without this arm a source
+		// opening with a block comment built under ww but failed
+		// coordinator discovery ("invalid or missing package
+		// clause"). An unterminated comment runs to EOF and the
+		// clause parse fails loud.
+		if (c == '/' && i + 1 < src.len && src[i + 1] == '*') {
+			i += 2;
+			for (i + 1 < src.len
+			    && !(src[i] == '*' && src[i + 1] == '/')) {
+				i += 1;
+			};
+			if (i + 1 >= src.len) { return src.len; };
+			i += 2;
+			continue;
+		};
 		break;
 	};
 	return i;