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> [!NOTE]
> **Medium Risk**
> Refactors wallet coin split/combine paths used by RPC; behavior should
be equivalent but touches core transaction construction and coin
selection.
>
> **Overview**
> Moves **split** and **combine** coin logic out of `WalletStateManager`
into a new **`FungibilityManager`**, wired on the state manager at
startup and used by the wallet RPC for `split_coins` / `combine_coins`.
>
> RPC handlers now resolve a fungible wallet via `get_fungible_wallet`
(standard or CAT only) and call the manager instead of
`wallet_state_manager.split_coins` / `combine_coins`. Invalid wallet
types raise **`Wallet {id} is not eligible for coin splitting`** (tests
updated for split and combine RPC paths). **`coin_num_limit`** is no
longer forwarded into the combine implementation; limits still apply via
`CombineCoins` request validation.
>
> Behavior of coin selection, fees, and transaction building is intended
to stay the same—this is primarily structural cleanup for LABS-490.
>
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
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code reviews on this repo. Configure
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Matt HauffandGitHub
9492119b2f