Return ODE step-limit failures through status

[krystophny]

Replace the terminal error stop on adaptive-step exhaustion with the existing per-call failure status. Context-aware callers may also supply a positive step limit and receive an optional integer status, so long constructions can bound the work and handle an exhausted solve without terminating the process. The default remains one million steps.

The failure flag is thread-private, matching the integrator state and preventing one OpenMP caller from observing another caller status. Successful trajectories, tolerances, Runge-Kutta coefficients, event handling, and returned states are unchanged. On exhaustion, the last accepted state is returned with odeint_has_failed() true and ierr=1, matching the existing step-underflow path. A later successful call resets both statuses.

Verification

Failing before, with the behavioral test applied to main:

fo: test failed: Error: There is no specific subroutine for the generic odeint_allroutines

Passing after:

test_odeint_allroutines_context PASS 0.06s
Static: OK (228 modules, 228 changed, 228 affected)
Build: OK
Tests: OK
Lint: OK
Fmt: WARN (two touched Fortran files)
All stages passed

The test forces a one-step exhaustion, checks both failure interfaces, then runs a successful solve and verifies that both statuses recover.