revert(build): restore python >=3.12 constraint

HPC module Python/3.12.3-GCCcore-13.3.0 satisfies >=3.12, so the
relaxation to >=3.11 was unnecessary. No package version changed.

configs/hpc/smoke_test.yaml

@@ -0,0 +1,12 @@
+# Minimal config to verify HPC setup is functional.
+# Run with: python src/train.py --config configs/hpc_smoke_test.yaml
+exp_name: "hpc_smoke_test"
+seed: 0
+track: true           # Test WandB integration
+capture_video: false  # No rendering for smoke test
+save_model: true      # Test the end-of-training save routine
+checkpoint_frequency: 0
+num_envs: 4
+total_timesteps: 10000
+num_steps: 64
+cuda: true