fix(curator): only mark agent-created for background-review sediment (#19621)

Tighten the provenance semantics added in #19618: skills a user asks a
foreground agent to write via skill_manage(create) now stay invisible to
the curator. Only skills the background self-improvement review fork
sediments through skill_manage get the created_by=agent marker.

- tools/skill_provenance.py — new ContextVar module mirroring the
  _approval_session_key pattern: set_current_write_origin / reset /
  get / is_background_review. Default origin is 'foreground'; the
  review fork sets 'background_review'.
- run_agent.py — run_conversation() binds the ContextVar from
  self._memory_write_origin at the top of each call. The review fork
  runs on its own thread (fresh context), so foreground and review
  contexts never cross-contaminate.
- tools/skill_manager_tool.py — skill_manage(action='create') now
  only calls mark_agent_created() when is_background_review(). All
  other cases (foreground create, patch, edit, write_file, delete)
  continue as before.
- tests: test_skill_provenance.py (6 tests covering the ContextVar
  surface), split test_full_create_via_dispatcher into foreground
  vs. review-fork variants, curator status tests now mark-first.

Why: the agent routinely edits existing user skills on the user's
behalf; those writes must never flip provenance. And when a user
explicitly asks the foreground agent to create a skill, that skill
belongs to the user. The curator should only be cleaning up after
its own autonomous sediment from the review nudge loop.

run_agent.py

@@ -10421,6 +10421,15 @@ class AIAgent:
         from hermes_logging import set_session_context
         set_session_context(self.session_id)
 
+        # Bind the skill write-origin ContextVar for this thread so tool
+        # handlers (e.g. skill_manage create) can tell whether they are
+        # running inside the background self-improvement review fork vs.
+        # a foreground user-directed turn. Set at the top of each call;
+        # the review fork runs on its own thread with a fresh context,
+        # so the foreground value here does not leak into it.
+        from tools.skill_provenance import set_current_write_origin
+        set_current_write_origin(getattr(self, "_memory_write_origin", "assistant_tool"))
+
         # If the previous turn activated fallback, restore the primary
         # runtime so this turn gets a fresh attempt with the preferred model.
         # No-op when _fallback_activated is False (gateway, first turn, etc.).