3.2 Reachability: a dungeon whose exit is unreachable from the entrance is
paid-but-unwinnable. generate() now BFS-checks entrance->exit and regenerates
if unreachable. Retries are deterministic (per-attempt ROT seed = seedInt +
attempt; the seeded rng stream keeps advancing), so verify-regeneration
replays the same attempts and reproduces the exact dungeon — the provably-fair
determinism from Phase 0.2 is preserved. The single-pass body is extracted to
_generateOnce and isReachable does the flood-fill.
3.3 Monster collision: with movesPerPlayerMove > 1 (the casino preset's 1.5x
speed) the monster takes multiple steps per turn, but collision was only
checked after the loop — so it could step onto the player's tile and off again
between checks, phasing through and missing the catch (player-favorable, erodes
the house edge). Collision is now checked after each sub-step.
Adds reachability tests (provablyFair.test.js) and monsterCollision.test.js.
Random block timing remains the untouched core mechanic. Full suite: 20 suites
/ 153 tests.