Fix None-value guard in get_n_calculated_per_process for Zig backend

[Copilot]

When using the Zig drop-in binary for bcrham, process_out_err initialises all bcrham_proc_info[i]['calcd'] fields to None (keys present, values absent) because the Zig binary emits no matching debug strings. The original guard checked for missing keys only, so during partition runs get_n_calculated_per_process would crash with TypeError: unsupported operand type(s) for +=: 'float' and 'NoneType'.

Changes

• get_n_calculated_per_process: change key-presence check ('vtb' not in procinfo['calcd']) to .get('vtb') is None, which catches both absent keys and None values — consistent with how the existing fallback comment describes the intent ("we lost some stdout somewhere")

# Before — misses None-valued keys initialised by process_out_err
if 'vtb' not in procinfo['calcd'] or 'fwd' not in procinfo['calcd']:

# After — catches both missing keys and None values
if procinfo['calcd'].get('vtb') is None or procinfo['calcd'].get('fwd') is None:

The guards added previously for print_partition_dbgfo and check_wait_times remain correct; this fixes the one unguarded caller that is exercised during partition (hierarchical agglomeration) rather than just annotation.

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