add some completion tests

[WindSoilder]

Description

❯ ls
╭───┬───────┬──────┬──────┬──────────╮
│ # │ name  │ type │ size │ modified │
├───┼───────┼──────┼──────┼──────────┤
│ 0 │ a.txt │ file │  0 B │ now      │
╰───┴───────┴──────┴──────┴──────────╯

❯ ls a.
NO RECORDS FOUND

There is a completion issue on previous version, I think @amtoine have reproduced it before. But currently I can't reproduce it on latest main.
To avoid such regression, I added some tests for completion.

[amtoine]

i'm trying it out on latest main... ♻️
could definitely reproduce on 0.93.0 at least

EDIT: yep, appears to be fixed on latest main, having a regression test sounds perfect 🙏

[sholderbach]

I think related are:

• fix: prevent relative directory traversal from crashing #12438
• Completions not working with files that have multiple periods in the name #12203