|  | Add 36 unit tests for cj/delete-buffer-and-file covering:
  - Normal cases: VC vs non-VC file deletion, trash flag usage
  - Boundary cases: file content variations, naming edge cases, buffer states
  - Error cases: permission issues, VC failures, error propagation
  Key testing decisions documented in Commentary:
  - Mock delete-file errors for deterministic, portable tests
  - Test our code's behavior (branching logic, error propagation), not the
    underlying trash/filesystem implementations
  - Verify correct calls to vc-delete-file vs delete-file with trash flag
  All 36 tests passing. |