enable individual-specific transition out of infectious state

current implementation of recovery function takes in a global constant rate of recovery, in a way consistent with ODE-driven compartmental model. This does not take advantage of the agent based set up, as the next big dev goal, we should change the recovery_function to enable each individual to have their own recovery probability dependent on input state (e.g., how long ago was infection acquired, underlying state of across-individual heterogeneity etc)

Start by locating the recovery_function implementation and the code that calls it in the agent-based model. Trace how infection timing and individual state are represented, then determine how the function should receive that input and produce an individual recovery probability. Done means individuals can recover according to their own input-dependent probabilities rather than one global recovery rate, with the existing model behavior checked.