Stop shut doors turning interior rooms into solid rock

[Justrada]

Caught by driving the deployed build — an interior came back as 56 rock and 64 floor. Interiors should have zero solid hexes; walls are edges specifically so a room costs no standable ground.

Cause

reachableFrom — the generator's connectivity check — treated a shut door as a barrier. So any room the spanning tree happened to gate with a closed door was judged unreachable, and the prune pass filled it with stone.

A closed door is a door. Someone opens it. Structural reachability blocks on walls and solid terrain only. Moment-to-moment passability is a different question, and the engine already answers it correctly through compileTerrain + reachableHexes, which do respect door state.

Why the tests missed it

Two reasons, both worth noting:

1. The existing "leaves no stranded hexes" test called the same helper, so it was self-consistent with the bug — it agreed that the walled-off rooms were unreachable, and the prune had already turned them to rock so they were no longer "open".
2. Doors are closed 25% of the time; with ~6 spanning-tree doors, roughly 1 seed in 5 rolls all-open. The seed the interior suite used was one of them.

New tests

• interior produces no solid hexes across 60 seeds
• every room stays reachable across 30 seeds with every door forced locked

Both fail against the old code and pass against this one — verified by reverting just the source and re-running.

440 tests green, typecheck and build clean.

🤖 Generated with Claude Code