Multiple free-space tiles can render an incomplete card

先从 src/lib/bingo.ts 和 src/lib/server/cardShuffle.ts 中 effectivePoolSize、getCardSize 和 pickCardWithFreeSpace 的流程开始，然后检查受影响的 bingo 和 tile-admin server 路由。复现一个包含两个 free-space tiles 的 25-tile pool，并比较 raw 和 effective 计数。完成标准是阻止或规范化无效配置，并且 /bingo 不再渲染少于 25 个单元格。

Problem

The admin UI permits multiple isFreeSpace tiles. effectivePoolSize subtracts every free space after the first, but getCardSize still returns the minimum size of 5. pickCardWithFreeSpace then drops all but one free-space tile and can return fewer than 25 cells. tooFewTiles uses the raw tile count, so it does not prevent rendering.

Reproduction

1. Create a 25-tile pool with two tiles marked Free.
2. Open /bingo.

The effective pool is 24, the selected card has 23 regular tiles plus one centered free space (24 total), and the UI renders only 24 cells in a 5-column grid. The core calculation reproduces as { effectivePoolSize: 24, cardSize: 5, renderedTiles: 24 }.

Suggested fix

Validate or enforce exactly zero or one free-space tile, or base the availability check on the effective pool and require cardSize ** 2 selected tiles before showing the board. The tile admin should prevent the invalid configuration or clearly normalize extra free spaces.

Affected code

• src/lib/bingo.ts
• src/lib/server/cardShuffle.ts
• src/routes/bingo/+page.server.ts
• src/routes/admin/tiles/+page.server.ts