feat(triggers): added ConvergenceFailureTrigger

added new trigger which throws on convergence failures. This also required adding a new "step" method for other triggers which gets called every step instead of every trigger throw. The ConvergenceFailureTrigger has sucsessgully let teh engine evolve to 10Gyr without any meaningful growth of convergence failures.

src/include/gridfire/solver/strategies/CVODE_solver_strategy.h

@@ -175,14 +175,24 @@ namespace gridfire::solver {
             const size_t num_steps;         ///< Number of CVODE steps taken so far.
             const DynamicEngine& engine;    ///< Reference to the engine.
             const std::vector<fourdst::atomic::Species>& networkSpecies; ///< Species layout.
+            const size_t currentConvergenceFailures; ///< Total number of convergence failures
+            const size_t currentNonlinearIterations; ///< Total number of non linear iterations
 
             /**
              * @brief Construct a context snapshot.
              */
             TimestepContext(
-                double t, const N_Vector& state, double dt, double last_step_time,
-                double t9, double rho, size_t num_steps, const DynamicEngine& engine,
-                const std::vector<fourdst::atomic::Species>& networkSpecies
+                double t,
+                const N_Vector& state,
+                double dt,
+                double last_step_time,
+                double t9,
+                double rho,
+                size_t num_steps,
+                const DynamicEngine& engine,
+                const std::vector<fourdst::atomic::Species>& networkSpecies,
+                size_t currentConvergenceFailure,
+                size_t currentNonlinearIterations
             );
 
             /**
@@ -281,7 +291,7 @@ namespace gridfire::solver {
         SUNLinearSolver m_LS = nullptr;   ///< Dense linear solver.
 
 
-        TimestepCallback m_callback;      ///< Optional per-step callback.
+        std::optional<TimestepCallback> m_callback;      ///< Optional per-step callback.
         int m_num_steps = 0;              ///< CVODE step counter (used for diagnostics and triggers).
 
         bool m_stdout_logging_enabled = true; ///< If true, print per-step logs and use CV_ONE_STEP.