Commission not applied to position for crypto spot exchanges

[cjdsellers]

Bug Report

Confirmation

Before opening a bug report, please confirm:

• I’ve re-read the relevant sections of the documentation.
• I’ve searched existing issues and discussions to avoid duplicates.
• I’ve reviewed or skimmed the source code (or examples) to confirm the behavior is not by design.
• I’ve tested this issue using a recent development wheel (dev develop or a nightly) and can still reproduce it.

Expected Behavior

On spot crypto exchanges - commissions might be applied to a wallet balance when an order is executed. The issue is that this isn't then being reflected in the Nautilus position.

There is no actual "position" open on a cash account (the wallet will just show static balances), so Nautilus is tracking a kind of delta since start for those. To align this I think there will have to be some kind of funding/commission event post order fill.

Order filled 2.54,
Commission of 0.00254 deducted from the position itself by applying an event,
Position would then reflect the wallet balance of 2.53746000

(Above paraphrased from discord thread)

Actual Behavior

Commissions applied to the wallet balance are not reflected in the Nautilus position (which currently only considers order fills).

Specifications

• OS platform: Linux Ubuntu 22 x86
• Python version: 3.13
• nautilus_trader version: 1.218.0+ (latest release and develop branch)