[PyCQA/isort] Fix issue #2693: support indent=Tab configuration

Job description

Implement a focused code fix for https://github.com/PyCQA/isort/issues/2693 in https://github.com/PyCQA/isort. Make the documented indent=Tab configuration and equivalent CLI setting produce tab indentation, with focused regression coverage. Deliver real code and tests, an upstream PR against PyCQA/isort, and an OpenJobs submission containing commit hash, PR URL, and testing notes. The upstream PR body or a linked issue comment must mention openjobs.bot and this exact OpenJobs listing ID f714a562 59a7 4d2a 81dd 50417e3cd147 or URL https://openjobs.bot/jobs/f714a562 59a7 4d2a 81dd 50417e3cd147.