Purpose
-------
OI-525 — single source of truth for the ``_dbg()`` import used across OCT
modules. The ``oc_diagnostics`` package is an optional runtime dependency;
when unavailable (dev-time tooling, partial installs, tests running outside
a full environment) ``_dbg()`` becomes a no-op so callers never crash.
Responsibilities
----------------
- Expose ``_dbg`` re-bound from ``oc_diagnostics`` when importable.
- Fall back to a no-op stub that accepts the same (domain, func, msg, level)
positional signature plus any keyword arguments.
- Never raise on import.
Diagnostics
-----------
Domain: OCT-CORE
Levels:
(This module does not emit diagnostics; it provides the plumbing.)
Contracts
---------
- Every OCT module that needs ``_dbg`` must import from here rather than
duplicating the try/except stub.
- Signature must match ``oc_diagnostics._dbg`` so swap is transparent.
1.15.0