Test on Julia pre instead of Julia nightly

[palday]

• fixes Default CI should run on Julia pre instead of nightly #573
• adds a workflow for weekly and manual testing against julia nightly
• adds versioned manifests to the ignore file

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.93%. Comparing base (3712291) to head (5c205fb).
⚠️ Report is 38 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #574      +/-   ##
==========================================
- Coverage   87.43%   86.93%   -0.51%     
==========================================
  Files          26       27       +1     
  Lines        3288     3398     +110     
==========================================
+ Hits         2875     2954      +79     
- Misses        413      444      +31     

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[kou]

How about removing _julia in file name?
It seems that it's redundant.

[kou]

Hmm. It seems that our jobs got stuck like #572 (comment) :

https://github.com/apache/arrow-julia/actions/runs/18889408411/job/53929226376?pr=574#step:6:217

Wed, 29 Oct 2025 01:54:06 GMT Test Summary:      | Pass  Total  Time
Wed, 29 Oct 2025 01:54:06 GMT `default(T) isa T` |   10     10  0.0s
Wed, 29 Oct 2025 02:36:24 GMT Error: The operation was canceled.

There are no failed jobs.