Bump the fresh pin to v0.40.0 #339

Problem

DESCRIPTION's Remotes: pins NewGraphEnvironment/fresh@v0.39.0, and fresh is at v0.40.0.

What v0.40.0 changes

fresh 0.40.0 (fresh#247) gives frs_point_snap() a breaking signature change. It now takes a whole dataset and returns watershed_group_code. frs_feature_find(points = <sf>) and frs_watershed_split() move to the same snap.

Checked 2026-10-14 against link@1e84df2: nothing in R/ or data-raw/*.R calls frs_point_snap(), frs_feature_find() or frs_watershed_split(). lnk_points_snap() mentions the frs_point_snap_knn conventions only in its roxygen.

Tasks

• Bump Remotes: to fresh@v0.40.0. Decide whether the Imports: floor (fresh (>= 0.38.0)) moves
• Full test suite against fresh 0.40.0
• One-WSG run to confirm the outputs are unchanged (prepare once, re-classify; CLAUDE.md "Full-run digests are not reproducible on main")
• Re-prep the cyphers before the next dispatch: the preflight checks fresh's symbols

Split out of #338 so that PR stays docs-only.