The "Promote pawn" dialog popped for any pawn "moved" toward the last
rank: the commit paths checked piece type + destination rank but never
the pawn's SOURCE rank. With the phantom layer now filling ranks 7-8
with tappable phantom pieces, tapping one (which falls through to the
real-move handler) while a real pawn was armed triggered the dialog for
a move no pawn could make — and for any phantom type, not just pawns.
Root cause: incomplete promotion detection, duplicated in Game.svelte
`onCommit` and the server's `isPromotionRequired`. Replaced with one
shared `isPromotionMove(piece, from, to)` — pawn, from the rank adjacent
to promotion, to the promotion rank, at most one file over — used by
both. 7 unit tests in packages/shared.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Adds a null-valued entry under a valid square key (d3) to the
'keeps valid entries and drops invalid ones' fixture, proving the
typeof/null guard branch in deserializePhantoms is exercised.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
claude (blind_chess)