FX2: wire no-moves reshuffle into the UI swipe-commit path

The rendered swipe-commit path (`plan_and_commit`) bypassed the turn-loop's
no-moves rule: a deadlocked board (no legal swap) stayed stuck on screen because
only `play_turn` checked `!has_legal_swap` and reshuffled, and the UI never calls
`play_turn`.

Factor the post-settle "no legal swaps -> reshuffle" check into a shared
`reshuffle_if_deadlocked` in board.sx and call it from BOTH `play_turn` and
`plan_and_commit`, so the animated UI commit obeys the identical model rule. The
reshuffle runs after the cascade settles (post-`commit_swap`); the AnimMove's
recorded `final` stays the settled pre-reshuffle board, so the cascade animation,
per-round audio, and input gating are unchanged — the reshuffled layout renders on
the next settled frame. No win/lose/turn-accounting change; a reshuffle spends no
move and no score.

Regression test tests/swipe_reshuffle.sx drives the exact UI path (swipe_intent ->
plan_and_commit) on the deadlocked board from tests/level.sx: before = no legal
swaps / in_progress; after = reshuffled (has_legal_swap true, 9 legal swaps, no
immediate match), score/moves/budget unchanged. It FAILS pre-fix (board stays
stuck, has_legal_swap false) and PASSES post-fix.

tests/expected/swipe_reshuffle.exit

@@ -0,0 +1 @@
+0

tests/expected/swipe_reshuffle.stdout

@@ -0,0 +1,23 @@
+== deadlocked board: UI swipe-commit path must reshuffle ==
+ROYGBPRO
+PROYGBPR
+BPROYGBP
+GBPROYGB
+YGBPROYG
+OYGBPROY
+ROYGBPRO
+PROYGBPR
+before: matches 0 legal_swaps 0 has_legal_swap false status in_progress
+intent (0,0)->(1,0)
+commit: legal false rounds 0 awarded 0
+after: matches 0 legal_swaps 9 has_legal_swap true status in_progress
+after: score 0 moves_made 0 moves_remaining 10
+BGGYORYR
+RRYGOPBY
+YRYBPRGB
+OOBGBPRG
+RPRPYRPO
+OBBPOOPG
+OBGGOPGY
+YPRYBORP
+ok: UI swipe-commit path reshuffles a deadlocked board