test/simulate_jumps: use setp instead of integrator.ps for callback param updates

JumpProcesses.SSAIntegrator does not expose a `ps` accessor (only
`derivative_discontinuity` is in its property list under SciMLBase v3),
so `integrator.ps[:k] = value` fails with FieldError. The four affected
callbacks were the actual cause of the 4 errors in
`Tests (*, Simulation)` jobs:

  Higher-order MAJ parameter updates (combinatoric=true)   — line 451
  Higher-order MAJ parameter updates (combinatoric=false)  — line 500
  Mixed-order MAJ parameter updates (combinatoric=true)    — line 545
  Combinatoric true/false equivalence (3X→Y)               — line ~645

Migration: capture the parameter setter via SymbolicIndexingInterface.setp
once at problem-construction time, then call it inside the callback. SII
is implemented on the integrator interface (not via getproperty), so it
flows through SSAIntegrator correctly:

    setk! = setp(jprob_cb, :k)
    function affect_cb!(integrator)
        setk!(integrator, 24.0)
        reset_aggregated_jumps!(integrator)
    end

This is the v3-canonical pattern for symbolically-indexed parameter
updates inside callbacks; same shape works on ODEIntegrator,
SDEIntegrator, and SSAIntegrator alike.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>

Author: ChrisRackauckas

test/simulation_and_solving/simulate_jumps.jl

@@ -2,6 +2,7 @@
 
 # Fetch packages.
 using Catalyst, JumpProcesses, ModelingToolkitBase, OrdinaryDiffEqTsit5, Statistics, Test
+using SymbolicIndexingInterface: setp
 
 # Sets stable rng number.
 using StableRNGs
@@ -447,8 +448,9 @@ end
     jprob_cb = JumpProblem(rn, u0, (0.0, 200.0), ps;
         aggregator = Direct(), save_positions = (false, false))
     condit(u, t, integrator) = t == 100.0
+    setk! = setp(jprob_cb, :k)
     function affect_cb!(integrator)
-        integrator.ps[:k] = 24.0
+        setk!(integrator, 24.0)
         reset_aggregated_jumps!(integrator)
     end
     cb = DiscreteCallback(condit, affect_cb!)
@@ -496,8 +498,9 @@ end
     jprob_cb = JumpProblem(rn, u0, (0.0, 200.0), ps;
         aggregator = Direct(), save_positions = (false, false))
     condit(u, t, integrator) = t == 100.0
+    setk! = setp(jprob_cb, :k)
     function affect_cb!(integrator)
-        integrator.ps[:k] = 24.0
+        setk!(integrator, 24.0)
         reset_aggregated_jumps!(integrator)
     end
     cb = DiscreteCallback(condit, affect_cb!)
@@ -541,8 +544,9 @@ end
     jprob_cb = JumpProblem(rn, u0, (0.0, 200.0), ps;
         aggregator = Direct(), save_positions = (false, false))
     condit(u, t, integrator) = t == 100.0
+    setk1! = setp(jprob_cb, :k1)
     function affect_cb!(integrator)
-        integrator.ps[:k1] = 24.0
+        setk1!(integrator, 24.0)
         reset_aggregated_jumps!(integrator)
     end
     cb = DiscreteCallback(condit, affect_cb!)
@@ -641,8 +645,10 @@ end
             aggregator = Direct(), save_positions = (false, false))
         condit(u, t, integrator) = t == 100.0
         new_k_true = 24.0
+        new_k_val = rn === rn_true ? new_k_true : new_k_true / factorial(3)
+        setk! = setp(jp, :k)
         function affect_equiv!(integrator)
-            integrator.ps[:k] = rn === rn_true ? new_k_true : new_k_true / factorial(3)
+            setk!(integrator, new_k_val)
             reset_aggregated_jumps!(integrator)
         end
         cb = DiscreteCallback(condit, affect_equiv!)