Add a guide on chunking in the executor

[ihincks]

Summary

This guide describes the chunk_size parameter on quantum program items, how auto-chunking works, etc.

Details and comments

AI tools used: claude opus 4.6

[TsafrirA]

This looks great.

[jyu00]

Thanks @ihincks, this is really helpful.

Quick question - there is no way to "front load" a shot loop with chunk_size, right? For example, if I have a program with two items: item A has 50 configurations, and item B has 30 configurations. I cannot force all 50 circuits from item A to run in one shot loop, and those from item B to run in a separate shot loop. I'd have to submit 2 different QuantumPrograms to do that?

[ihincks]

@jyu00 that's correct

[diego-plan9]

Thanks - @ihincks , are there plans of retaking this PR?

[jyu00]

We can add this to the IQP Guides cc @beckykd