Add `# Why largest-remainder?` section to `calc.rs` module doc

[Kingsman-99]

Description

contracts/split/src/calc.rs has a terse //! comment but does not explain why the largest-remainder method is used over simple floor division. Adding a //! # Why largest-remainder? section explaining rounding and the sum == total invariant would make the module self-sufficient for new contributors.

Acceptance Criteria

• Expand the //! module doc in contracts/split/src/calc.rs with a # Why largest-remainder? section
• Explain: floor division leaves up to n-1 stroops undistributed; LR assigns them to recipients with the largest fractional remainders
• Include a one-line numeric example (e.g. distributing 10 among 3 equal shares gives [4, 3, 3])
• cargo doc builds without warnings
• cargo test passes

Context

• Target file: contracts/split/src/calc.rs

[emirykl]

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Hey, I want to take that issue

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[ademolacomfort]

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Hi, can I work on this issue

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[Philo016]

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Can i be assigned to this?

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[dimin4241-svg]

@dimin4241-svg has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi! I’ve worked with Rust/Soroban documentation and rounding logic. I understand the task: explain why largest-remainder is used, including invariants and tie-breaking, while keeping the examples aligned with the implementation. I can submit and verify this focused docs change within a few hours. Please assign this issue to me.

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[laddyr141-ui]

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i would love to work on this

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