siblings.py and shape-doctor.py: a dangling Windows junction at ../<Project> still reads as an empty slot, because #784's dangling-link rule asks only is_symlink(), which is False for a junction; also ask os.path.isjunction, as family_link does #793

Goal: on Windows, make siblings and the doctor both name a dangling junction at ../<Project> as a dangling link, as #784 (PR #788) makes them name a dangling symlink.

Filed by lane openRepoShape-3 under v1.1.1, on Brett Heap's word of 2026-10-16T13:35:28Z ("yes create v1.1.1"). Lane 3's reviewer RV-d raised it as N2 on #788 (#788 (comment)).

What is known:

• siblings.py and shape-doctor.py: a link to nothing at ../<Project> is NOT A CLONE, reported and left as it is, so the dry run no longer says would clone where the real run ends CLONE FAILED, and the doctor's members row no longer calls the slot absent (#784) #788 (head e966a684) tells a dangling link from an empty slot with Path.is_symlink(), in two places: shape-doctor.py's unclonable and siblings.py's slot check.
• On Windows, is_symlink() is False for a junction. CPython 3.12 added os.path.isjunction as a separate call for that reason.
• So siblings.py and shape-doctor.py: a link to nothing at ../<Project> is NOT A CLONE, reported and left as it is, so the dry run no longer says would clone where the real run ends CLONE FAILED, and the doctor's members row no longer calls the slot absent (#784) #788's rule still reads a dangling junction as an empty slot: the dry run says "would clone" and the doctor says absent. That is siblings.py (make siblings) and the doctor: a dangling symlink at ../<Project> reads as an empty slot, so the dry run says "would clone" and the doctor says absent, while the real run ends CLONE FAILED #784's bug, for a junction.
• Not measured: what the real clone does onto a dangling junction. Lane 3 has no Windows machine, and CI is Linux-only since ci: run the test suite on Linux only #597.
• Precedent:
  • siblings.py:931 already asks getattr(os.path, "isjunction", lambda _: False) in family_link.
  • tests/test_family_siblings_placement.py:564-574 tests that on Linux by patching os.path.isjunction.

What to do:

• At both places where siblings.py and shape-doctor.py: a link to nothing at ../<Project> is NOT A CLONE, reported and left as it is, so the dry run no longer says would clone where the real run ends CLONE FAILED, and the doctor's members row no longer calls the slot absent (#784) #788 asks is_symlink(), also ask the junction check, spelled as family_link spells it. Python before 3.12 has no isjunction, so the fallback says no.
• Keep the doctor and make siblings in agreement on the wording.
• Tests: patch os.path.isjunction to say yes for the slot path, as test_family_siblings_placement.py does. Assert that the dry run, the real run's refusal and the doctor's row all word it as dangling.

Lands after #788 (#784).