Add remote SSH execution support for GPU nodes

Adds --remote [user@]host flag to obliterate, run, and tourney commands,
enabling execution on remote GPU nodes via SSH. Also supports a remote:
section in YAML configs. The remote runner handles SSH connectivity checks,
GPU detection, auto-installation of obliteratus, log streaming, and result
syncing back to the local machine via scp.

examples/remote_gpu_node.yaml

@@ -0,0 +1,41 @@
+# Example: Run an ablation study on a remote GPU node via SSH.
+#
+# Usage:
+#   obliteratus run examples/remote_gpu_node.yaml
+#
+# The 'remote' section tells Obliteratus to SSH into the specified host,
+# install obliteratus if needed, run the pipeline there, and copy results
+# back to the local machine.
+#
+# You can also use --remote on any command instead of a YAML section:
+#   obliteratus obliterate meta-llama/Llama-3.1-8B-Instruct --remote root@gpu-node --ssh-key ~/.ssh/id_rsa
+
+model:
+  name: meta-llama/Llama-3.1-8B-Instruct
+  task: causal_lm
+  dtype: float16
+  device: auto
+
+dataset:
+  name: wikitext
+  split: test
+  max_samples: 500
+
+strategies:
+  - name: layer_removal
+    params:
+      layer_indices: [10, 11, 12]
+
+metrics: [perplexity]
+batch_size: 8
+max_length: 512
+output_dir: results/remote_example
+
+remote:
+  host: gpu-node.example.com
+  user: root
+  port: 22
+  ssh_key: ~/.ssh/id_rsa
+  remote_dir: /tmp/obliteratus_run
+  python: python3
+  sync_results: true