chore: updates CI runners and handles failing Windows test

[rosygmiki]

This PR temporarily skips an issue where Windows builds fails when source files are missing. It also cleans up our CI workflow by removing unsupported platforms.

Tests

• Skips the missing source file test on Windows.
• Includes a bug fix which changes nil to err and adds a new test function for the added error path to satisfy Codecov patch % requirement.

Chores

• Removes CI workflow support for macOS on Intel and Windows on ARM.
• Updates go.mod and README badge with Go 1.26.

Closes #84

[gemini-code-assist]

Code Review

This pull request fixes a bug in pkg/tar-patch/apply.go where an error encountered while closing the current file was being ignored and nil was returned instead of the actual error. The code has been corrected to return the err. There are no review comments to address.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.61%. Comparing base (752790f) to head (9810239).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #101      +/-   ##
==========================================
+ Coverage   81.43%   81.61%   +0.17%     
==========================================
  Files          10       10              
  Lines        1115     1115              
==========================================
+ Hits          908      910       +2     
+ Misses        117      116       -1     
+ Partials       90       89       -1     

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[djach7]

A couple of change requests, thanks for working on this!

[djach7]

Possible change, feel free to ignore if you think this is out of scope for the PR.

I think the change to err here is good, but looking at this harder there's a potential leak in the following scenario:

• the close fails on line 68
• we set currentFile to nil on line 69
• we return the err on line 71 but we now have a file that's still open without a way to reference it because we set the reference to nil

I asked Claude about it and it fired off this suggested fix:

      if f.currentFile != nil {
          err := f.currentFile.Close()
          if err != nil {
              // Don't nil out currentFile if close fails
              return fmt.Errorf("failed to close current file: %w", err)
          }
          f.currentFile = nil
      }
      currentFile, err := os.Open(filepath.Join(f.basePath, file))
      if err != nil {
          return err
      }
      f.currentFile = currentFile
      return nil
  }

Again, I know you didn't make any changes here other than the nil -> err one so if you want to kick this to a later PR or issue that's fine. I just spotted it and wanted to call it out

[djach7]

I think it would be beneficial to add a little more of a "why" to this comment, just a line or two explaining why we're skipping windows for now