dual_decomposition: extend strengthened conjecture table to n=20

n=19 (21,138 col., 68s) and n=20 (107,874 col., 361s) both pass.
New total for clauses (1)-(4) over n<=20: 142,812/142,812.

Also bump max_n in check_conj_3_8_scaled.py default to 20 (was 18) and
time_budget_per_n to 7200s.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

papers/dual_decomposition_minimal_counterexamples/paper.aux

@@ -26,10 +26,10 @@
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 \newlabel{conj:face-monochromatic-pair-strengthened}{{4.3}{10}}
 \newlabel{rem:conj-3-8-empirical}{{4.4}{10}}
-\newlabel{rem:implication-4ct}{{4.5}{10}}
 \newlabel{tocindent-1}{0pt}
 \newlabel{tocindent0}{0pt}
 \newlabel{tocindent1}{17.77782pt}
 \newlabel{tocindent2}{0pt}
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+\newlabel{rem:implication-4ct}{{4.5}{11}}
 \gdef \@abspage@last{11}