Snap guard excludes wetland connectors (1410) — should only exclude subsurface (1425)

[NewGraphEnvironment]

Problem

.frs_snap_guards() excludes both edge_type 1410 (network connector) and 1425 (subsurface flow) from KNN snap queries. But 1410 segments are real wetland connectivity (77K total, 204K waterbody-associated in wetlands) — users should be able to snap to a point in a wetland.

Only 1425 (subsurface flow — 343 total, genuinely underground) should be excluded by default. And even that should be overridable.

Filed upstream: NewGraphEnvironment/bcfishpass#8

Proposed Solution

1. Remove 1410 from .frs_snap_guards() — only exclude 1425 by default
2. Add exclude_edge_types parameter to frs_point_snap():

# Default: only exclude subsurface (1425)
frs_point_snap(conn, pts)

# Override: snap to everything
frs_point_snap(conn, pts, exclude_edge_types = NULL)

# Custom exclusion
frs_point_snap(conn, pts,
  exclude_edge_types = frs_edge_types(category = "subsurface")$edge_type)