feat(runtime): enforce governed mutation boundaries

Assistant: codex
Assistant-Model: gpt-5.6-sol
Assistant-Session: 01a06ba0-10aa-7ea0-b20a-4f3fac39efe9

rein_aharness/fi_research_brief.py

@@ -420,20 +420,6 @@ def run_fi_research_brief(
                 )
                 committed = True
             head_after = _git(repo, "rev-parse", "HEAD")
-            # Best-effort push so workstation / Forgejo see the brief.
-            # Diverged branches must not fail the run; log via reason only if push fails
-            # after a successful write.
-            if committed and os.environ.get("FI_RESEARCH_BRIEF_PUSH", "1").strip().lower() not in {
-                "0",
-                "false",
-                "no",
-                "off",
-            }:
-                try:
-                    _git(repo, "push", "origin", "HEAD")
-                except FiResearchBriefError:
-                    # Leave brief committed locally; operators reconcile git separately.
-                    pass
         except FiResearchBriefError as exc:
             result = FiResearchBriefResult(
                 ok=False,