IF_curr_delta ignores initial value of v and cannot record v (NEST)

[apdavison]

With the NEST backend, IF_curr_delta ignores the initial membrane potential and cannot record v. Calling record('v') on an IF_curr_delta population raises NESTErrors.IllegalConnection: Cannot connect with unknown recordable v, and the value passed via initial_values={'v': ...} is not applied. Both iaf_psc_delta (on_grid) and iaf_psc_delta_ps (off_grid) are affected.

Minimal reproduction:

import pyNN.nest as sim
sim.setup(timestep=0.1)
cell = sim.Population(1, sim.IF_curr_delta(v_rest=-65.0, v_thresh=-50.0),
                      initial_values={'v': -65.0})
cell.record('v')     # raises IllegalConnection
sim.run(10.0)

Environment: PyNN master (0.13.0); NEST 3.10.0; Python 3.14