fix(engine): single-word rule connects along the play line

Bumps the engine to scrabble-solver v1.1.1, where a single-word-per-turn play
must form its word along its own line through an existing tile: a multi-tile play
that touches the board only perpendicular to itself (the contour РЮМ/КЕД/ОР cases)
no longer connects. For a single tile that abuts the board on both axes the engine
now plays the higher-scoring legal orientation instead of the geometrically longer
one (playDirection), so a real word is never rejected in favour of a non-word.

Reworks the single-word solver/engine tests for the corrected rule (no longer a
superset of standard play) and updates ARCHITECTURE/FUNCTIONAL/PRERELEASE.

docs/FUNCTIONAL.md

@@ -93,7 +93,8 @@ takes the empty seat after **1.5–3 minutes**, so a game always starts — and
 you can close the app while you wait and come back later. For Russian games (auto-match or friend
 invitation), New Game also offers **"Multiple words per turn"** (default **off**): off plays
 the simplified **single-word rule** — only the word laid along the player's line must be a
-real word, and any incidental perpendicular words are ignored and not scored — while on is
+real word (and it must still cross or extend letters already on the board along that line),
+and any incidental perpendicular words are ignored and not scored — while on is
 standard Scrabble. English games are always standard and show no such toggle. In auto-match
 the choice joins the pairing key, so a player only meets opponents who picked the same rule. Friend games (2–4) are
 formed by inviting players from the friend list (an invitation, like a friend code,