Switch 32 bit accessors to 64 bit accessors

[swahtz]

📋 Originally created by @fwilliams

Original author: @fwilliams
Date: 2025-07-06T11:45:15Z

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We're hitting scaling issues due to 32 bit integer limits. We should start switching our accessors to be 64 bit and make sure we're using int64_t index types. Let's use this issue to keep track of places where this needs to be done.

[swahtz]

💬 Comment by @fwilliams

Original author: @fwilliams
Date: 2025-07-06T11:45:47Z

@swahtz can you update the issue with your notes on this?

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📝 This comment was originally posted by @fwilliams and copied during issue migration