feat(ledger): quiet idle outbox polling

tests/application/test_ledger_outbox.py

@@ -1,6 +1,7 @@
 """LedgerOutbox + LedgerWriter direct unit tests (REQ-019)."""
 from __future__ import annotations
 
+import logging
 from dataclasses import replace
 from datetime import UTC, datetime, timedelta
 
@@ -132,6 +133,80 @@ def test_writer_exposes_claim_and_outcome_counters():
     assert writer.counters["outcome:completed"] == 1
 
 
+def test_idle_day_is_silent_and_counted_per_instance(caplog):
+    writers = [
+        LedgerWriter(
+            InMemoryLedgerOutbox(instance_key=instance_key),
+            InMemoryLedger(),
+            instance_key=instance_key,
+        )
+        for instance_key in ("instance-a", "instance-b")
+    ]
+
+    with caplog.at_level(logging.INFO, logger="trex_core.application.ledger_outbox"):
+        for writer in writers:
+            for _ in range(86_400):
+                writer.run_once()
+
+    assert [
+        writer.metrics_snapshot()["claims"]["empty_polls_total"]
+        for writer in writers
+    ] == [86_400, 86_400]
+    assert "claim_result=empty" not in caplog.text
+    assert "correlation_ids" not in caplog.text
+
+
+def test_nonempty_claim_log_has_ordered_json_correlation_ids(caplog):
+    outbox = InMemoryLedgerOutbox(instance_key="inst-a")
+    writer = LedgerWriter(outbox, InMemoryLedger(), instance_key="inst-a")
+    first = outbox.enqueue(_trade(execution_id="e-1"))
+    second = outbox.enqueue(_trade(execution_id="e-2"))
+
+    with caplog.at_level(logging.INFO, logger="trex_core.application.ledger_outbox"):
+        writer.run_once(limit=2)
+
+    claim_logs = [
+        record.getMessage()
+        for record in caplog.records
+        if "ledger outbox claim:" in record.getMessage()
+    ]
+    assert claim_logs == [
+        "ledger outbox claim: instance_key=inst-a claim_result=claimed "
+        f"count=2 limit=2 correlation_ids=[\"{first.correlation_id}\","
+        f"\"{second.correlation_id}\"]"
+    ]
+
+
+def test_metrics_snapshot_is_complete_and_detached():
+    outbox = InMemoryLedgerOutbox(instance_key="inst-a")
+    writer = LedgerWriter(outbox, InMemoryLedger(), instance_key="inst-a")
+
+    snapshot = writer.metrics_snapshot()
+
+    assert snapshot == {
+        "available": True,
+        "scope": "process_lifetime",
+        "instance_key": "inst-a",
+        "claims": {
+            "empty_polls_total": 0,
+            "claimed_batches_total": 0,
+            "unavailable_total": 0,
+            "lost_total": 0,
+            "foreign_instance_total": 0,
+        },
+        "outcomes": {
+            "completed_total": 0,
+            "duplicate_completed_total": 0,
+            "retryable_failure_total": 0,
+            "conflict_blocked_total": 0,
+            "permanent_failure_total": 0,
+            "dead_lettered_total": 0,
+        },
+    }
+    snapshot["claims"]["empty_polls_total"] = 999
+    assert writer.metrics_snapshot()["claims"]["empty_polls_total"] == 0
+
+
 @pytest.mark.parametrize("instance_key", ["", "   "])
 def test_writer_rejects_explicit_empty_instance_key(instance_key):
     outbox = InMemoryLedgerOutbox(instance_key="inst-a")