fix(rithmomachia): validate move path before showing capture error on hover

Fixed capture error tooltip not showing by adding path validation before
checking for invalid capture relations.

The hover error now correctly:
1. Validates the move path is legal (using validateMove)
2. Only shows if path is valid AND there's no valid capture relation
3. Prevents showing errors for moves that aren't even possible

Added import for validateMove from pathValidator utils.

This ensures the "no valid relation" tooltip only appears when you're
hovering over an enemy piece that your selected piece can legally move to,
but cannot capture due to missing valid numeric relations.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

apps/web/src/arcade-games/rithmomachia/components/board/BoardDisplay.tsx

@@ -10,6 +10,7 @@ import { usePieceSelection } from '../../hooks/usePieceSelection'
 import { useRithmomachia } from '../../Provider'
 import type { Piece, RelationKind } from '../../types'
 import { getSquarePosition } from '../../utils/boardCoordinates'
+import { validateMove } from '../../utils/pathValidator'
 import { getEffectiveValue } from '../../utils/pieceSetup'
 import {
   checkDiff,
@@ -454,6 +455,10 @@ export function BoardDisplay() {
 
     if (!moverPiece || !targetPiece) return false
 
+    // First check if the move path is valid
+    const validation = validateMove(moverPiece, selectedSquare, hoveredSquare, state.pieces)
+    if (!validation.valid) return false
+
     const moverValue = getEffectiveValue(moverPiece)
     const targetValue = getEffectiveValue(targetPiece)