ww: implement local vendor package semantics

internal/wwpackage/package.ww

@@ -45,6 +45,7 @@ type pkgplan = struct {
 	identity: str,
 	root: str,
 	workdir: str,
+	workdircreated: bool,
 	buildout: str,
 	builderr: str,
 	start: i32,
@@ -726,15 +727,21 @@ fn pkgsetplanpaths(p: *pkgplan, groups: []pkggroup, root: str, index: i32,
 	p.root = strings.concat(root, "/plan-", num);
 	if (!pkgmakedir(p.root)) { return false; };
 	p.workdir = "";
+	p.workdircreated = false;
 	if (workroot.len != 0) {
 		// Canonical request-directory identity makes equivalent spellings and
 		// product reorderings select one command-scoped driver workdir.
 		p.workdir = strings.concat(workroot, "/",
 			pkgworkkey(p.sourceroot));
-		match (os.mkdirs(p.workdir, 448)) {
+		match (os.mkdirs(workroot, 448)) {
 		case void => void;
 		case let e: os.oserror => return false;
 		};
+		let mr: i32 = os.mkdir(p.workdir, 448i32);
+		if (mr == 0) { p.workdircreated = true; }
+		else if (mr != -17 || !pkgisdir(p.workdir)) {
+			return false;
+		};
 	};
 	p.buildout = strings.concat(p.root, "/build.stdout");
 	p.builderr = strings.concat(p.root, "/build.stderr");
@@ -1466,6 +1473,15 @@ export fn packagecommand(args: []str) int = {
 	i = 0;
 	for (i < plans.len) {
 		failed += pkgemitplan(&plans[i], groups, compileonly);
+		// The driver commits its tool stamp only after semantic preflight. If
+		// this request minted the persistent directory and rejection left it
+		// unstamped, reclaim it only if it is still empty. A concurrent or
+		// interrupted writer's contents are never recursively removed.
+		if (plans[i].workdircreated
+			&& !os.exists(strings.concat(plans[i].workdir, "/.wwtool.stamp"))) {
+			let rr: i32 = os.rmdir(plans[i].workdir);
+			if (rr != 0 && rr != -2) { failed += 1; };
+		};
 		i += 1;
 	};
 	if (!pkgremoveall(tmproot)) {