fix(journey): show foreground-created skills in /journey via learn provenance marker

record_created now stamps created_by="learn" on foreground creates
(e.g. /learn) instead of leaving it unset, and the learning-graph filter
honors "learn" alongside "agent"/used. "learn" is a learning-signal
marker only: curator management stays keyed strictly on "agent"
(_is_curator_managed_record), so user-taught skills appear in /journey
without becoming eligible for autonomous curation.

Fixes #111317.

---
authored with AI assistance (Muse, Meta's Muse Spark) under the contributor's direction; the contributor reviewed the diff and ran the tests.

tests/tools/test_skill_manager_tool.py

@@ -432,10 +432,11 @@ class TestSkillManageDispatcher:
             usage = load_usage()
         result = json.loads(raw)
         assert result["success"] is True
-        # No provenance marker on a foreground create — record either missing
-        # entirely (telemetry best-effort) or present with created_by unset.
+        # Foreground create carries the "learn" learning-signal marker — never the
+        # curator-management opt-in ("agent"), and the record may be missing
+        # entirely (telemetry best-effort).
         rec = usage.get("test-skill") or {}
-        assert rec.get("created_by") in {None, "", False}
+        assert rec.get("created_by") in {"learn", None, "", False}
 
     def test_successful_mutations_emit_lifecycle_with_correlation(self, tmp_path):
         with (