remove: drop ckpt_weight_density_per_run.png figure

The per-run weight density figure contained misleading legacy
iteration labels (500k/1M iter) that contradicted the paper's
stated token budgets (15B). Removing it avoids confusion; the
per-category density plot (ckpt_weight_density.png) and Table 7
remain as the primary evidence.

main.tex

@@ -547,17 +547,6 @@ spread.}
 \label{fig:ckpt_weight_density}
 \end{figure}
 
-\begin{figure}[H]
-\centering
-\includegraphics[width=0.95\linewidth]{data/ckpt_weight_density_per_run.png}
-\caption{Per-checkpoint weight density breakdowns. The three checkpoints
-are \texttt{norm-15bt} (AdamW, Normal init, 15B tokens), \texttt{kami-15bt}
-(AdamW, GPT-2 residual scaling, 15B tokens), and \texttt{muon-25bt}
-(Muon, 25B tokens). Note: the iteration labels inside the figure reflect
-legacy script metadata and should be ignored in favour of the token
-budgets stated here.}
-\label{fig:ckpt_weight_density_per_run}
-\end{figure}
 
 % ======================================================================
 \section{Conclusion}