Add coho habitat pipeline with DB-side classification

[NewGraphEnvironment]

Summary

Habitat model pipeline — extract, enrich, break, classify, aggregate — all on PostgreSQL. Proves the workflow on the Byman-Ailport subbasin before scaling to full Neexdzii study area.

New functions

• frs_edge_types() — FWA edge type lookup from bundled CSV (41 codes from GeoBC User Guide)
• frs_col_join() — generic lookup table enrichment (channel_width, MAD, upstream_area, any key)

Enhanced functions

• frs_classify(where=) — scope classification by SQL predicate (edge_type, waterbody_key, accessible)
• frs_network(to=) — write results to DB working tables instead of pulling to R memory
• frs_break_find(where=, append=) — filter points_table rows, combine multiple break sources
• frs_point_snap(exclude_edge_types=) — configurable snap guard (only exclude subsurface 1425, not wetland connectors 1410)

Bundled data

• parameters_habitat_thresholds.csv — bcfishpass defaults (11 species)
• parameters_habitat_method.csv — MAD vs channel_width per watershed group
• parameters_fresh.csv — access gradients + spawn gradient mins
• edge_types.csv + feature_codes.csv — FWA reference tables

Vignette: Classifying Coho Habitat on the Byman-Ailport Subbasin

• Full pipeline: network → col_join → col_generate → break (gradient + falls) → classify (accessible, spawning, rearing, lake rearing) → aggregate
• Access barriers from gradient thresholds AND barrier falls
• Lake rearing gap: bcfishpass scores 0 km, fresh recovers habitat
• Scenario comparison: spawn gradient min at 0%, 0.5%, 1.0%

Issues

• Fixes Add frs_col_join() for generic lookup table enrichment #51 (frs_col_join)
• Fixes Snap guard excludes wetland connectors (1410) — should only exclude subsurface (1425) #52 (snap guard)
• Fixes Add access gradient thresholds (parameters_habitat_access.csv) #54 (access gradient params)
• Relates to Add frs_break() for network geometry splitting with find/validate/apply decomposition #38 (frs_break table + points modes)
• Relates to Add to= parameter to frs_network() for DB-side pipeline #53 (frs_network to=)
• Relates to Add spawn/rear gradient min to habitat thresholds CSV #55 (spawn gradient min)
• Relates to barriers_subsurfaceflow lumps network connectors (1410) with subsurface flow (1425) bcfishpass#8 (1410 vs 1425)

Test plan

• 505 tests pass (devtools::test())
• devtools::check() — 0 errors, 0 warnings
• All three vignettes render from cache
• Habitat vignette rendered from live DB

Relates to NewGraphEnvironment/sred-2025-2026#16