The board grammar already parses per-part marks ([N marks] / "Total for Question
N is M marks"), but they were dropped building the first-pass template and the
row mapper hardcoded max_marks=0 — so every born-digital paper came back with
zero marks for a teacher to re-key by hand.
Thread the parsed mark through: bands.py derive_bands now carries each part's
`marks`, template.build passes it into part_bands, and _map_first_pass_to_rows
reads it via a defensive _safe_marks (non-negative int; unknown/None -> 0, so
image-only OCR — which has no marks yet — is unchanged). Containers still roll up
from parts. Adds test_auto_map_surfaces_born_digital_part_marks.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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