Fix callback override syntax

Use Hydra add-override syntax for every_n_epochs in the new large-run submitters.

This matches the latest progress-checkpoint script alignment on main and keeps callback composition valid.

Author: sgreenbury

slurm_scripts/ablations/vit_mae_pretrain/submit_vit_mae_pretrain_large.sh

@@ -103,7 +103,7 @@ for datamodule in "${!EXPERIMENTS[@]}"; do
             trainer.max_time="${BUDGET_MAX_TIME}" \
             +trainer.max_epochs="${cosine_epochs}" \
             trainer.callbacks.0.every_n_train_steps_fraction=0.05 \
-            trainer.callbacks.0.every_n_epochs=0 \
+            +trainer.callbacks.0.every_n_epochs=0 \
             trainer.callbacks.0.save_top_k=-1 \
             trainer.callbacks.0.filename=\"snapshot-{progress_token}-{epoch:04d}-{step:08d}\"
     done

slurm_scripts/ablations/vit_mae_pretrain/submit_vit_mae_to_crps_large.sh

@@ -134,7 +134,7 @@ for datamodule in "${!EXPERIMENTS[@]}"; do
             trainer.max_time="${BUDGET_MAX_TIME}" \
             +trainer.max_epochs="${cosine_epochs}" \
             trainer.callbacks.0.every_n_train_steps_fraction=0.05 \
-            trainer.callbacks.0.every_n_epochs=0 \
+            +trainer.callbacks.0.every_n_epochs=0 \
             trainer.callbacks.0.save_top_k=-1 \
             trainer.callbacks.0.filename=\"snapshot-{progress_token}-{epoch:04d}-{step:08d}\"
     done