test: pin the orphan policy contract for solved plans

Component tests for the graph-integrity check. Test-only.

- the normal shape: ``python.depends == ["pip"]`` makes ``pip``
  reachable and it inherits python's category without rescue;
- the abnormal shape: ``python.depends == []`` orphans ``pip`` and
  hard-fails -- named as broken solver metadata in the docstring;
- ``CONDA_LOCK_ALLOW_ORPHANED_LOCKFILE=1`` semantics: WARNING
  naming ``main``, ``--dev-dependencies``/``-e <category>``, and
  the envvar itself (so the message cannot silently weaken),
  orphans promoted to ``main``, no raise;
- the classic conda#896 corrupt-cache shape (``zlib`` planned with
  empty depends, unreachable) hard-fails with the regeneration
  guidance and the escape hatch named in the error;
- a multi-category dependency-breakage variant;
- a positive intact-graph sanity check.

Verification: ``pytest tests/component/test_graph_integrity.py``.
Each test drives the public ``solve_conda`` path with a synthetic
dryrun, so the contract holds at the orchestration boundary rather
than only on the helper.

Author: claude