fix: Dereference symlinks in deploy tarball (-h flag)

Mix creates priv/ directories as symlinks to deps/. Without -h,
tar archives the symlink which breaks on the remote (points to
a path that doesn't exist). The -h flag follows symlinks and
archives the actual files.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 2 people

lib/terrarium/runtime.ex

@@ -221,7 +221,7 @@ defmodule Terrarium.Runtime do
       end)
 
     try do
-      case System.cmd("tar", ["czf", tarball_path | file_args], stderr_to_stdout: true) do
+      case System.cmd("tar", ["czf", tarball_path, "-h" | file_args], stderr_to_stdout: true) do
         {_, 0} ->
           Logger.debug("Tarball created",
             sandbox_id: sandbox.id,