mobile 0.3.4 hotfix

mobile 0.3.4 hotfix

highlights

• fixed the mobile invalid prompt error when continuing chats with file or attachment history
• tightened server-side message cleanup before streaming so only valid model messages reach the AI SDK
• keeps file and image turns instead of dropping them just because they have little or no text
• includes the 0.3.4 custom model, alternative API, and prompt caching changes