Remove redundant Daley-Kendall model reference from SIS section and add it to SIR section for clarity and improved organization.

Author: Daniel Precioso, PhD

modules/networks/index.qmd

@@ -144,8 +144,6 @@ We simulate:
   Susceptible → Infected → Recovered
   Permanent immunity.
 
-If you want one extra reference beyond SIR, a classical rumor counterpart is the **Daley-Kendall** model (Ignorant → Spreader → Stifler), where spreaders become stiflers after contact with spreaders/stiflers [@daley1965stochastic].
-
 Key questions you will answer:
 
 * How does network structure affect epidemic size?

modules/networks/sir.qmd

@@ -48,11 +48,15 @@ $$
 In SIS, $I \to S$ (you become susceptible again). In SIR, $I \to R$ (you become immune). That single change completely changes the *long-term* behavior.
 :::
 
-## A key rigorous fact (absorbing states)
+### Related Rumor Model
+
+If you want one extra reference beyond SIR, a classical rumor counterpart is the **Daley-Kendall** model (Ignorant -> Spreader -> Stifler), where spreaders become stiflers after contact with spreaders/stiflers [@daley1965stochastic].
+
+## Absorbing States
 
 On a finite graph with $\mu > 0$, the process reaches a time $T$ such that there are **no infected nodes** ($I(T)=0$), and after that nothing can ever change [@keeling2008modeling; @pastor2015epidemic].
 
-Intuition (but still rigorous): each node can become infected **at most once** (because $R$ is permanent), so there can be at most $N$ infection events. Since recovery happens with positive probability, infections cannot persist forever.
+Each node can become infected **at most once** (because $R$ is permanent), so there can be at most $N$ infection events. Since recovery happens with positive probability, infections cannot persist forever.
 
 This means SIR always ends in a "frozen" configuration containing only $S$ and $R$ nodes.