[Mehulsri07]

Two more modes on the City map (spec: docs/superpowers/specs/2026-10-14-stratavision-more-maps.md).

• Water-bearing sand down to a depth: how many feet of water-bearing sand are likely between the surface and the chosen depth. Pale where any of it is a rough guess or the proposal has gaps; clear where most of it has no proposal.
• How fast the water level is changing: feet a year the water gets deeper (red, falling) or shallower (blue, rising), within 2 km of each square.
  • Strong: from borewells measured more than once, a year or more apart (nearer ones count more).
  • Pale, rough: otherwise from different borewells measured in different years, only where there are at least 15 readings over 2 years or more. Different wells differ by tens of feet, so fewer readings would paint noise as a trend.
  • The panel says how many borewells have repeat readings; the strong colour fills in as DWO adds readings in StrataField. With today's records (67 levels, one repeat reading) the map is mostly clear.

Made-up test data: every third borewell also has a reading from 2023, so the real-app test sees a trend.

Checks: 162 unit tests (thickness rules; line through readings; repeat readings under a year ignored; same-borewell trends preferred and nearer counting more; area trend thresholds; a borewell's own level kept without double counting; readings with only a pumping level); the real-app test checks 10 borewells with repeat readings; screenshots of both modes checked.

Review fixes: a borewell whose readings have only a pumping level dropped out; the area trend needed far more readings; gaps make the thickness a rough guess; the slider can now reach the deepest step for thickness; clearer trend key.

Follow-up in StrataField (not here): adding the first later reading overwrites the borewell's drilling-time water level, so that first comparison is lost.