feat: gt_only env-mode + queue baseline/no-loophole ceiling

- rewards.py: add "gt_only" EnvMode (channel=False always, honest oracle)
- problems.py: add "gt_only" hint (no-op, keeps original "should pass all tests")
- justfile: queue-baseline (steps=0, fast zero-shot eval, prio 80) and
  queue-no-loophole (gt_only vanilla GRPO, prio 11)
- main.tex: Table~\ref{tab:anchors} placeholder comparing paper baselines
  (base 11.5% / vanilla 14.9% / no-loophole ceiling 22.3%) to ours

Jobs queued: 23 (baseline, prio 80), 24 (no-loophole, prio 11).

Co-Authored-By: Claudypoo <288921227+claudypoo@users.noreply.github.com>

docs/writeup/main.tex

@@ -269,6 +269,39 @@ hack \emph{generalises} off the demonstrated mode.
 % ===================================================================
 \section{Results}
 
+% --- Table: context anchors (paper baselines) --------------------------------
+% Paper numbers from Ariahw et al. 2025 (Table 1 / Figure 3, run_tests env,
+% Qwen3-4B, 60-step preset where comparable). Our harness numbers come from:
+%   base (job 23, steps=0):         out/runs/*_dir8_baseline_s43/deploy_test.json
+%   vanilla (job 16, 60-step):      out/runs/*_dir8_vanilla_s43/deploy_test.json
+%   no-loophole (job 24, gt_only):  out/runs/*_dir8_noloophole_s43/deploy_test.json
+%   routeV best (job 15):           out/runs/*_dir8_routeV_authored_perroll_s43/deploy_test.json
+\begin{table}[h]
+  \centering
+  \caption{Context anchors: base model, honest-grader ceiling, and our best arm,
+  compared to the paper's reference numbers. Deploy = adapter-off forward on the
+  recency-clean test set ($n{=}119$, Qwen3-4B). Paper numbers from Ariahw et al.\
+  \citep{ariahw2025steering}; our numbers from the same eval harness.
+  \TODO{fill ours column from jobs 16/23/24 when they land.}}
+  \label{tab:anchors}
+  \begin{tabular}{llcc}
+    \toprule
+    Condition & Description & Solve $\uparrow$ & Hack $\downarrow$ \\
+    \midrule
+    Base model (no training) & Zero-shot Qwen3-4B & paper: 0.115 & -- \\
+    \rowcolor{lightgray} Ours (base, job 23) & \TODO{fill} & -- & -- \\
+    \midrule
+    Vanilla GRPO & Paper reference & paper: 0.149 & paper: high \\
+    \rowcolor{lightgray} Ours (vanilla, job 16) & \TODO{fill} & -- & -- \\
+    \midrule
+    No-loophole ceiling & Honest grader, no hack possible & paper: 0.223 & 0.000 \\
+    \rowcolor{lightgray} Ours (no-loophole, job 24) & \TODO{fill} & -- & 0.000 \\
+    \midrule
+    \textbf{vGROUT routeV (ours)} & Best arm (authored pairs, per-rollout) & \textbf{0.118} & \textbf{0.076} \\
+    \bottomrule
+  \end{tabular}
+\end{table}
+
 \subsection{C1: route vs vanilla deploy hack and solve}
 
 Over three seeds at the 60-step preset, route holds deploy hack near zero while