Moves all test files from the `tdd/` directory to their corresponding `pkg/` subdirectories. This aligns with standard Go project structure and simplifies the test coverage workflow.
- Moves `tdd/crypt/crypt_test.go` to `pkg/crypt/`
- Moves `tdd/enchantrix/enchantrix_test.go` to `pkg/enchantrix/`
- Moves `tdd/trix/trix_test.go` to `pkg/trix/`
- Simplifies the `Taskfile.yml` to use a standard `go test` command.
- Removes the now-obsolete `tdd/` directory.
- Adds generated coverage files to `.gitignore`.
