polish: cross-reference verification and final formatting

- Fix overfull hbox in ch05 method comparison table (118pt -> resolved)
- Fix overfull hbox in ch09 verification equation (147pt -> split with align)
- Fix overfull hbox in ch08 phase plane table (16pt -> p-column width)
- Fix overfull hbox in appA VOP formula (70pt -> inline textstyle)
- Fix overfull hbox in appB Fourier series table (70pt -> resizebox)
- Fix overfull hbox in appB common integrals table (tabular width)
- Fix overfull hbox in appB Laplace properties table (tabular width)
- Fix float too large in ch06 TikZ resonance figure (scale + clip)
- Fix text overfull in ch03 terminal velocity paragraph
- Fix ch09 summary table width with @{} column specifiers

chapters/ch05_second_order_nonhomogeneous.tex

@@ -723,17 +723,17 @@ Both undetermined coefficients (UC) and variation of parameters (VoP) find parti
 \centering
 \caption{Undetermined coefficients vs.\ variation of parameters}
 \label{tab:ch05_method_comparison}
-\begin{tabular}{l l l}
+\begin{tabular}{p{2.8cm} p{4.8cm} p{6.2cm}}
   \toprule
   \textbf{Aspect} & \textbf{Undetermined Coefficients} & \textbf{Variation of Parameters} \\
   \midrule
-  Applicable $g(x)$ & Polynomials, $e^{\alpha x}$, $\sin(\beta x)$, $\cos(\beta x)$, and their sums/products & \emph{Any} continuous $g(x)$ (in principle) \\
-  Requires $y_h$? & Only for overlap check (modification rule) & Yes --- need a full fundamental set \\
+  Applicable $g(x)$ & Polynomials, $e^{\alpha x}$, $\sin/\cos(\beta x)$, sums/products & \emph{Any} continuous $g(x)$ (in principle) \\
+  Requires $y_h$? & Only for overlap check & Yes --- need a full fundamental set \\
   Requires $W(x)$? & No & Yes \\
   Normalized form? & Not required & \textbf{Required} (coefficient of $y''$ must be~1) \\
   Computation & Algebra (solve linear system) & Integration (may be difficult or non-elementary) \\
   Speed (simple $g(x)$) & Fast --- algebraic, no integrals & Slower --- integrals needed \\
-  Speed (complex $g(x)$) & \textbf{Not applicable} --- method fails & Always applicable (if integrals exist) \\
+  Speed (complex $g(x)$) & \textbf{N/A} --- method fails & Always applicable (if integrals exist) \\
   \bottomrule
 \end{tabular}
 \end{table}