ClaudeandClaude Opus 5.5
118635aebd
One _index helper guards block_cell (block, y, x), slot (block_cell, q) and map_cut_links (fluid_idx, dir) before addressing; previously e.g. block_cell(-1, 0, 0) returned -49 and fractional values were truncated. Adds focused rejection tests and Astra's one-block seam reproducer (build(4,8,4,8), receiver (2,0), dir 2 -> west-halo slot 90). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>