Purpose
-------
OI-519 regression tests — :func:`oct.core.octrc.load_octrc` and its silent
wrapper :func:`load_octrc_safe` must be the single source of truth for
``.octrc.json`` reads. This test exercises the contract that multiple
historical readers (linter, formatter, health, typecheck) now rely on.
Responsibilities
----------------
- Missing file → ``({}, [])``; ``load_octrc_safe`` → ``{}``.
- Valid JSON object → parsed dict, no errors.
- Invalid JSON → ``({}, [<error>])``.
- Non-object top-level JSON (e.g. a list) → ``({}, [<error>])``.
- OSError on read → ``({}, [<error>])``.
Diagnostics
-----------
Domain: CORE-TESTS
Levels:
L2 — test lifecycle
L3 — assertion details
L4 — deep tracing
Contracts
---------
- All file reads and writes use ``tmp_path``; no real ``.octrc.json``
is touched.