Default bundle: drop lake-adjacency requirement on SK upstream spawning

[NewGraphEnvironment]

Problem

bcfishpass's SK upstream-spawning rule DBSCAN-clusters candidate
spawning segments and credits only clusters within 2 m of a rearing-lake
polygon (load_habitat_linear_sk.sql lines 137–253).
Reaches separated from the lake by non-spawn connector segments (steep
sections, sub-cw, beaver complexes) get dropped — even when fish can
demonstrably reach them.

Known issue, not a bug surfaced here. Sockeye spawn well above nursery
lakes in tributaries that don't form lake-adjacent clusters.

Behaviour change requested

Default bundle: credit any segment that passes the spawn rule and is
upstream-accessible from a rearing lake. No cluster-must-touch-lake
gate. Distance from the lake is irrelevant — accessibility is the only
constraint.

bcfishpass bundle: unchanged. Continues to mirror bcfp lake-adjacent
clustering for parity testing.

Notes

• The 3 km downstream-of-outlet rule (spawn_connected_distance_max
  etc. in dimensions.csv) is unrelated and continues for both bundles.
• bcfp's lake-adjacency is hard-coded in SQL, not parameterized via
  dimensions.csv — a per-bundle switch needs to flow through the rules
  pipeline (or fresh's clustering helper).

Versions

• link: 0.19.0
• fresh: 0.25.0
• bcfishpass: 440bc1e (2026-04-28)
• fwapg: local Docker (port 5432)