Preserve offline game state when user logs in

[Copilot]

When a user plays offline and then authenticates, the in-progress game was being reset to a fresh board.

Changes

Track game state via ref to avoid callback churn

• Added currentGameRef synced via useEffect
• Prevents load callback recreation while maintaining access to current game state
• Uses match state directly (no ref needed since it's null in offline mode)

Preserve game on offline→online transition

• Detect transition: authUserUid && !match
• Skip reset if game has progress: status is Moving/GameOver or board differs from default
• Upload preserved state to Firebase when creating new match

Example scenario:

// User plays offline, rolls dice, makes moves
// currentGame.status === Status.Moving
// match === null

// User logs in → onAuthStateChanged fires
// load() called with authUserUid
// shouldPreserveGame === true
// setGame(newGame()) skipped, Firebase updated with currentGame

The preservation logic is scoped to only the offline→online transition; other scenarios (logout, friend switching, initial login) follow existing reset behavior.

Original prompt

preserve offline game state when the user logs in

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[ProLoser]

@copilot are you sure you need to store the match object? I'm pretty sure that's not used in offline games

[Copilot]

@copilot are you sure you need to store the match object? I'm pretty sure that's not used in offline games

You're right! The match ref wasn't needed since match is always null in offline games. I've simplified the code to use the match state directly. See commit 8333438.