add_line(snap_to_polygons=...) is accepted, documented, and ignored

[rhugman]

ConceptualMesh.add_line accepts a snap_to_polygons parameter and documents it:

def add_line(self, geometry, line_id, resolution, snap_to_polygons=True, is_barrier=False, ...):
    """
    snap_to_polygons (bool): If True, the line's endpoints will be snapped to
        nearby polygon boundaries to ensure connectivity.
    """

The value is never stored. The dict appended to self.raw_lines has no snap_to_polygons key, so nothing downstream can read it:

self.raw_lines.append({
    'geometry': geometry,
    'line_id': line_id,
    'lc': resolution,
    'is_barrier': is_barrier,
    'dist_min': dist_min,
    'dist_max': dist_max,
    'straddle_width': straddle_width
})

_enforce_connectivity then snaps every line unconditionally:

for i, line_data in enumerate(self.raw_lines):
    original_line = line_data['geometry']
    snapped_line = snap(original_line, poly_boundaries, tolerance)
    self.raw_lines[i]['geometry'] = snapped_line

So snap_to_polygons=False silently does nothing — the line is snapped anyway. A user who deliberately wants a line left un-snapped (for instance a line intentionally ending just short of a zone edge) gets the opposite of what they asked for, with no warning.

Options

1. Implement it — store the flag and skip those lines in _enforce_connectivity. This is what the docstring already promises.
2. Remove it — drop the parameter and the docstring entry, and document that all lines are snapped with connectivity_tolerance.

Option 1 is probably worth it: connectivity_tolerance is global, so per-feature opt-out is the only way to exempt a single line today.

Pre-existing on develop — not introduced by #12, though #12 adds connectivity_tolerance as a generate() override, which makes the missing per-feature control more noticeable.