docs: Fix mismatch of default dock position setting in project panel (#61971)

# Objective

Fixes #56277, the document-source mismatch of the default dock position
setting in project panel.
I also have found that the visual customization guide has the same
issue, so this PR fixes it too.

## Solution

I have updated the corresponding markdown files.

## Testing

I have tested the updated documents by rendering them in my local.

## Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

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Release Notes:

- N/A
58a3c0fa0e9rum committed on 7/31/2026, 7:38:17 AM· committed by GitHubparent5f180e0
2 files changedLine totals unavailable