fix: ensure ci artifacts are present when using devtool sandbox

Without ensure_ci_artifacts called inside cmd_sandbox, you will see an
index out of bounds errors during set up of the argument parser, since
build/img will be an empty directory (e.g. there are no kernels to
select, and the -1 index will be out of bounds).

Reported-by: Jack Thomson <[email protected]>
Signed-off-by: Patrick Roy <[email protected]>

tools/devtool

@@ -890,6 +890,7 @@ cmd_sh() {
 
 cmd_sandbox() {
     cmd_build --release
+    ensure_ci_artifacts
     cmd_sh "tmux new env PYTEST_ADDOPTS=--pdbcls=IPython.terminal.debugger:TerminalPdb PYTHONPATH=tests IPYTHONDIR=\$PWD/.ipython ipython -i ./tools/sandbox.py $@"
 }