fix(test): add back `main` test

[adamperkowski]

Description

Resolves #29

• Brings back the run test (as described in #29)
• Adds proper error handling when calling run() and buffer.toOwnedSlice()

How Has This Been Tested?

zig build test --summary all:

Build Summary: 10/10 steps succeeded
test cached
├─ run main-tests cached
│  └─ zig test main-tests Debug native cached 18ms MaxRSS:80M
│     └─ options cached
├─ run file-tests cached
│  └─ zig test file-tests Debug native cached 21ms MaxRSS:80M
│     └─ options (reused)
├─ run gen-tests cached
│  └─ zig test gen-tests Debug native cached 18ms MaxRSS:80M
│     └─ options (reused)
└─ run wav-tests cached
   └─ zig test wav-tests Debug native cached 21ms MaxRSS:80M
      └─ options (reused)

Types of Changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [x] Refactor (refactoring production code)

Checklist:

• [x] My code follows the code style of this project.
• [ ] I have updated the documentation accordingly.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.