Configurable list columns via header right-click

Native checkable menu on the column headers toggles Size, Modified,
Kind, Rights, Owner and Group (persisted, both panels). Owner/group
come from the ls-style SFTP longname remotely and cached uid/gid
lookups locally (POSIX; undefined on Windows). All columns sort.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/bun/fs/local.ts

@@ -11,6 +11,42 @@ function typeOf(st: Stats): EntryType {
 	return st.isDirectory() ? "dir" : "file";
 }
 
+/**
+ * uid/gid -> names, cached per process (a listing usually has 1-3 owners).
+ *
+ * PORTABILITY: POSIX-only lookups (`id -nu` works on macOS and Linux; group
+ * names use dscacheutil on macOS, getent elsewhere). On Windows these return
+ * undefined and the Owner/Group columns show "—".
+ */
+const idNameCache = new Map<string, string | undefined>();
+
+function resolveId(kind: "user" | "group", id: number): string | undefined {
+	if (process.platform === "win32") return undefined;
+	const cacheKey = `${kind}:${id}`;
+	if (idNameCache.has(cacheKey)) return idNameCache.get(cacheKey);
+	let name: string | undefined;
+	try {
+		const cmd =
+			kind === "user"
+				? ["id", "-nu", String(id)]
+				: process.platform === "darwin"
+					? ["dscacheutil", "-q", "group", "-a", "gid", String(id)]
+					: ["getent", "group", String(id)];
+		const proc = Bun.spawnSync(cmd, { stdout: "pipe", stderr: "ignore" });
+		if (proc.success) {
+			const out = proc.stdout.toString();
+			if (kind === "user") name = out.trim() || undefined;
+			else if (process.platform === "darwin") name = /^name:\s*(.+)$/m.exec(out)?.[1]?.trim();
+			else name = out.split(":")[0]?.trim() || undefined;
+		}
+	} catch {
+		// lookup tool missing — fall through to the numeric id
+	}
+	name ??= String(id);
+	idNameCache.set(cacheKey, name);
+	return name;
+}
+
 function toEntry(name: string, full: string, st: Stats): FileEntry {
 	return {
 		name,
@@ -19,6 +55,8 @@ function toEntry(name: string, full: string, st: Stats): FileEntry {
 		size: st.size,
 		mtime: st.mtimeMs,
 		mode: st.mode & 0o7777,
+		owner: resolveId("user", st.uid),
+		group: resolveId("group", st.gid),
 	};
 }