Katan: no roads past an opponent's settlement, piece limits, stable layout

Rules
- A road may only start from a crossing where the player has a building, or
  where one of their roads ends AND no opponent's settlement or city stands.
  roadConnects ignored opponents' buildings, so a road (the computer's included)
  could be laid straight past a settlement. Also applies to Road Building.
- Enforce the piece supply: 15 roads, 5 settlements, 4 cities. It was
  unlimited.
- Tests: building past a settlement and a city, free roads, own settlement not
  blocking, and running out of each piece.

UI
- The layout rescaled the board whenever it became the player's turn, because
  the action buttons only existed then. Everything outside the board now has a
  fixed height: the action bar always shows every button (disabled, not absent),
  the prompt is pinned to two lines, player cards always draw every line, and
  the dice total is always present. Rule recorded in docs/UI-catan.md.

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

docs/RULES-catan.md

@@ -159,7 +159,19 @@ its edge.
 A settlement goes on an **empty vertex** at least two edges from every standing
 building and connected to the seat's own road network. A city upgrades one of
 the seat's own settlements. A road goes on an empty edge that connects to the
-seat's network (a road or a building at one of its ends).
+seat's network: it must start from a crossing where the seat has a building, or
+where one of its roads ends.
+
+**An opponent's settlement or city on a crossing breaks the network there.** A
+road cannot be laid past it, even from a crossing where one of your own roads
+ends — only a crossing you own a building on is a way through. The same rule
+applies to the free roads of a Road Building card, and it is the same wall that
+cuts Longest Road (below).
+
+**Pieces are limited**: each player has **15 roads, 5 settlements and 4 cities**.
+A player who has laid them all cannot build another of that kind. Raising a
+settlement into a city returns the settlement to the supply, so the five
+settlements remain available to be laid again.
 
 The development deck is the published 25 cards: **14 Knights, 2 Road Building,
 2 Monopoly, 2 Year of Plenty, 5 Victory Point**. Cards are bought blind from the