chore(submodule): bump ontology-management-base to latest main

Advance the pinned OMB submodule from eb49b92 (v0.1.4-10) to 9ac9106
(v0.1.6-18-g9ac9106), the current tip of ASCS-eV/ontology-management-base main.

33 commits: OpenLABEL v2 v1-v2 gap closure, ODD subclass hierarchy, deterministic
LinkML pipeline, SHACL per-resource + check-failing-tests validation modes, and
context-generator fixes. No changes required in the engine itself.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: jdsika