Katan: playable screen, setup options, dev-preview catalogue gate

Adds the Katan screen on top of the WALA-119 engine, built in separable layers
so the look, wording, layout and interaction can each be changed alone:

- CatanStyle: every colour and proportion (light/dark), via LocalCatanStyle
- CatanText: every word on screen (pure functions of state)
- CatanGeometry: lattice -> pixels and tap hit-testing (pure, unit-tested)
- CatanInteraction: what is tappable and what a tap means, derived only from the
  engine's legal-move list (pure, unit-tested)
- CatanBoardView / CatanPanels / CatanDialogs: stateless composables
- CatanScreen: wiring to MatchController, portrait and landscape layouts
- CatanPreviews: Android Studio previews of real positions
- docs/UI-catan.md: how to adapt each layer, rules of the road, known gaps

Wiring: PlayScreen branch, GameSetupScreen options (3-4 players, game to
5/8/10/12), and a GameDescriptor.devPreview flag so dev builds can open Katan
while production still hides it until two-device play is verified.

Tests: CatanGeometryTest, CatanInteractionTest, CatanTextTest, CatalogTest.

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01JdMNbY5hLR7FjtfEE712xG

docs/README.md

@@ -42,6 +42,8 @@ Naming: the catalogue id, lowercase, e.g. `crazy8s` → `RULES-crazy8s.md`.
 
 - Build, CI, releases and OTA are described in the CI section of the root
   [README](../README.md).
+- [UI-catan.md](UI-catan.md) — how the Katan screen is layered, and how to restyle,
+  re-copy or re-lay-out it without touching the rules.
 - `licenses/` — third-party licences that must travel with the app
   (Uncial Antiqua under the SIL OFL; the app itself is GPL-3.0, see `/LICENSE`).
 - Repo-level agent notes live in [`CLAUDE.md`](../CLAUDE.md) at the root.