sync: taskd.trust parameter is ignored

### Describe your issue

When configuring task server the app asks to choose file or paste content of .taskrc. Either way when I give it config with option `taskd.trust=ignore hostname` it is not preserved in final config.

It is only my guess that in my particular case missing trust parameter is the problem. The guess is based on knowledge that my setup needs that option (doesn't work without it), and that it is not there in config after save.
I have made sure this works on other clients, like foreground on android and official binary ver. 2.6.2 on desktop

### Steps to reproduce

Confgure taskd server
Issue self-signed certificate with arbitrary (wrong) domain
Copy certs and cred to client with taskwarrior-flutter
Configure sync. Give it taskrc file (with `taskd.trust=ignore hostname` option) and certs. It will show no errors (if everything done right)
Tap at "Taskrc file is verified". It will show config, "trust" parameter is missing
Try to sync. It will show no errors. However nothing is synced.

### What was the expected result?

Sync is expected to work, or at least show any errors.

### Put here any screenshots or videos (optional)

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### How can we contact you (optional)

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### Would you like to work on this issue?

None

### By submitting this issue, I have confirmed that:

- [X] I have starred the repo ⭐ and watched 👀 it on GitHub and followed the contribution guidelines.

まず、taskd の同期設定で使用される taskrc のインポートと検証のフローを追跡します。taskd.trust=ignore hostname を使ってセットアップを再現し、その後、保存された設定が同期試行に至るまでを追跡します。trust パラメーターが保持され、同期が成功するか、有用なエラーが報告されれば完了です。

索引モデルが issue の本文から書いたものです。