fix(windows): use 0 for file mode on Windows (zig 0.16.0 compat)

zig 0.16.0 changed std.fs.File.Permissions on Windows from an
options struct (with .toMode() returning a POSIX mode integer)
to an enum (Windows-specific DWORD). Calling .toMode() on
Windows now fails to compile with:

  src\archiver.zig:97:65: error: no field or member function
  named 'toMode' in 'Io.File.Permissions__enum_2757'

Fix: write 0 for the file mode on Windows. POSIX mode bits
don't apply there, and the archive is read on the same machine
that wrote it, so the receiver can derive permissions from its
own filesystem.

On non-Windows platforms, keep the existing behavior of
writing @intcast(stat.permissions.toMode()).

Author: gilbertwong96

src/archiver.zig

@@ -94,7 +94,16 @@ pub fn pack_directory(arena: Allocator, path: []const u8, archive_path: []const
             if (stat.size > 0) {
                 assert(stat.size == try reader.streamRemaining(writer));
             }
-            try writer.writeInt(usize, @intCast(stat.permissions.toMode()), .little);
+            // On Windows, std.fs.File.Permissions is an enum (no
+            // .toMode() method), and POSIX mode bits don't apply.
+            // Write 0 — the archive is read on the same machine that
+            // wrote it, so the receiver can derive permissions from
+            // its own filesystem.
+            const mode: usize = if (builtin.os.tag == .windows)
+                0
+            else
+                @intCast(stat.permissions.toMode());
+            try writer.writeInt(usize, mode, .little);
 
             count += 1;