[00200200]

Addresses the descriptor-counting and inode-reuse portion of #864. This does not attempt to fix the other FreeBSD failures discussed there.

Before relying on /dev/fd or /proc/self/fd, check that the listing includes a newly opened descriptor. If neither view does, scan the SC_OPEN_MAX range. Share this helper between both descriptor counters and the inode-reuse fixture, so a standard-stream-only listing cannot hide a live descriptor or simulate reuse while an inode is still held open.

The regressions exercise complete, partial, missing and proc-only directory views using real open/duplicated descriptors and an unlinked file. Nine of the original twelve cases fail before the fix. Library implementation code is unchanged.

Validation on macOS/Python 3.13.4:

• Full suite: 2,808 passed, 163 skipped, no test failures.
• After adding a fixture passthrough control, targeted checks: 16 passed, 1 skipped. The supplemental run uses a long temporary path to exercise the existing macOS Unix-socket skip branch.
• Combined coverage and diff coverage: 100% (73 changed executable lines).
• Ruff check/format, Ty with the project's type dependencies, and whitespace checks pass.

Native FreeBSD has not been tested.