Ablation: pin gpt-5.5 @ ai.gahow.org (chat.completions); re-read token per arm

- Pin endpoint.model=gpt-5.5, base_url=https://ai.gahow.org/v1, wire_api=chat.completions
  in both ablation specs so both arms uniformly use the current ~/.codex model (the
  prior runs used the stale ai.prism.uno/gpt-5.4 that config.toml has since moved off).
- run_ablation_pair_d1.sh re-reads the codex token from auth.json right before each arm
  instead of capturing it once at launch (the stale-at-use capture 401'd naive 2/3).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

configs/examples/dash0_qwen27b_ablation_harness_on.json

@@ -168,7 +168,9 @@
     "max_history_trials": 8,
     "endpoint": {
       "provider": "codex",
-      "model": "gpt-5.4",
+      "model": "gpt-5.5",
+      "base_url": "https://ai.gahow.org/v1",
+      "wire_api": "chat.completions",
       "stream": true,
       "api_key_env": "OPENAI_API_KEY",
       "timeout_s": 180

configs/examples/dash0_qwen27b_ablation_naive_off.json

@@ -168,7 +168,9 @@
     "max_history_trials": 8,
     "endpoint": {
       "provider": "codex",
-      "model": "gpt-5.4",
+      "model": "gpt-5.5",
+      "base_url": "https://ai.gahow.org/v1",
+      "wire_api": "chat.completions",
       "stream": true,
       "api_key_env": "OPENAI_API_KEY",
       "timeout_s": 180