fix(cron): bump skill usage when cron jobs load skills

Cron jobs that reference skills via their skills: config never bumped
the usage counters in .usage.json, so the curator could auto-archive
skills actively used by cron jobs based on stale timestamps.

Now _build_job_prompt() calls bump_use(skill_name) for each
successfully loaded skill so the curator sees them as active.

tests/cron/test_scheduler.py

@@ -1857,6 +1857,54 @@ class TestBuildJobPromptMissingSkill:
         assert "go" in result
 
 
+class TestBuildJobPromptBumpUse:
+    """Verify that cron jobs bump skill usage counters so the curator sees them as active."""
+
+    def test_bump_use_called_for_loaded_skill(self):
+        """bump_use is called for each successfully loaded skill."""
+
+        def _skill_view(name: str) -> str:
+            return json.dumps({"success": True, "content": f"Content for {name}."})
+
+        with patch("tools.skills_tool.skill_view", side_effect=_skill_view), \
+             patch("tools.skill_usage.bump_use") as mock_bump:
+            _build_job_prompt({"skills": ["alpha", "beta"], "prompt": "go"})
+
+        assert mock_bump.call_count == 2
+        calls = [c[0][0] for c in mock_bump.call_args_list]
+        assert "alpha" in calls
+        assert "beta" in calls
+
+    def test_bump_use_not_called_for_missing_skill(self):
+        """bump_use is NOT called when a skill fails to load."""
+
+        def _missing_view(name: str) -> str:
+            return json.dumps({"success": False, "error": "not found"})
+
+        with patch("tools.skills_tool.skill_view", side_effect=_missing_view), \
+             patch("tools.skill_usage.bump_use") as mock_bump:
+            _build_job_prompt({"skills": ["ghost"], "prompt": "go"})
+
+        assert mock_bump.call_count == 0
+
+    def test_bump_failure_does_not_break_prompt(self, caplog):
+        """If bump_use raises, the prompt still builds — error is logged at DEBUG."""
+
+        def _skill_view(name: str) -> str:
+            return json.dumps({"success": True, "content": "Works."})
+
+        with patch("tools.skills_tool.skill_view", side_effect=_skill_view), \
+             patch("tools.skill_usage.bump_use", side_effect=RuntimeError("boom")), \
+             caplog.at_level(logging.DEBUG, logger="cron.scheduler"):
+            result = _build_job_prompt({"skills": ["good-skill"], "prompt": "go"})
+
+        # Prompt should still contain the skill content and original instruction
+        assert "Works." in result
+        assert "go" in result
+        # The error should be logged at DEBUG level, not crash
+        assert any("failed to bump" in r.message for r in caplog.records)
+
+
 class TestSendMediaViaAdapter:
     """Unit tests for _send_media_via_adapter — routes files to typed adapter methods."""