feat(consolidation): debounced gate for task body consolidation

New services/consolidation.py module with maybe_consolidate() — the
debounced trigger gate. Two reasons:

- log_added: gated by DEFAULT_LOG_THRESHOLD (3) counted since the task's
  consolidated_at timestamp.
- task_closed: bypasses the count gate; fires whenever status flips to
  done/cancelled.

Both reasons gated by the auto_consolidate_tasks user setting (default
on). Per-task asyncio.Lock prevents two simultaneous passes for the same
task. consolidate_task is a stub here — full implementation in the next
commit.

tests/test_consolidation.py

@@ -0,0 +1,108 @@
+"""Tests for the task-body consolidation pipeline (gate + full pass).
+
+Design: docs/superpowers/specs/2026-05-13-task-as-durable-record-design.md
+"""
+from unittest.mock import AsyncMock, patch
+
+
+# ── Gate logic ───────────────────────────────────────────────────────────────
+
+
+async def test_maybe_consolidate_below_threshold_does_not_fire():
+    """log_added with only 2 logs since last pass → no consolidation."""
+    from fabledassistant.services import consolidation
+
+    with patch.object(
+        consolidation, "_logs_since_last_consolidation",
+        new=AsyncMock(return_value=2),
+    ), patch.object(
+        consolidation, "consolidate_task", new=AsyncMock(),
+    ) as mock_consolidate, patch.object(
+        consolidation, "_auto_consolidate_enabled", new=AsyncMock(return_value=True),
+    ):
+        await consolidation.maybe_consolidate(
+            user_id=1, task_id=42, reason="log_added",
+        )
+
+    mock_consolidate.assert_not_awaited()
+
+
+async def test_maybe_consolidate_at_threshold_fires():
+    """log_added with N logs since last pass → consolidation scheduled."""
+    from fabledassistant.services import consolidation
+
+    # asyncio.create_task is the actual scheduler; replace it so the test
+    # doesn't need an event-loop background task to settle.
+    with patch.object(
+        consolidation, "_logs_since_last_consolidation",
+        new=AsyncMock(return_value=3),
+    ), patch.object(
+        consolidation, "_auto_consolidate_enabled", new=AsyncMock(return_value=True),
+    ), patch(
+        "fabledassistant.services.consolidation.asyncio.create_task",
+    ) as mock_create_task:
+        await consolidation.maybe_consolidate(
+            user_id=1, task_id=42, reason="log_added",
+        )
+
+    mock_create_task.assert_called_once()
+
+
+async def test_maybe_consolidate_task_closed_always_fires():
+    """task_closed bypasses the log-count gate."""
+    from fabledassistant.services import consolidation
+
+    with patch.object(
+        consolidation, "_logs_since_last_consolidation",
+        new=AsyncMock(return_value=0),
+    ), patch.object(
+        consolidation, "_auto_consolidate_enabled", new=AsyncMock(return_value=True),
+    ), patch(
+        "fabledassistant.services.consolidation.asyncio.create_task",
+    ) as mock_create_task:
+        await consolidation.maybe_consolidate(
+            user_id=1, task_id=42, reason="task_closed",
+        )
+
+    mock_create_task.assert_called_once()
+
+
+async def test_maybe_consolidate_setting_off_blocks_both_reasons():
+    """auto_consolidate_tasks=false → neither trigger fires."""
+    from fabledassistant.services import consolidation
+
+    with patch.object(
+        consolidation, "_logs_since_last_consolidation",
+        new=AsyncMock(return_value=5),
+    ), patch.object(
+        consolidation, "_auto_consolidate_enabled", new=AsyncMock(return_value=False),
+    ), patch(
+        "fabledassistant.services.consolidation.asyncio.create_task",
+    ) as mock_create_task:
+        await consolidation.maybe_consolidate(
+            user_id=1, task_id=42, reason="log_added",
+        )
+        await consolidation.maybe_consolidate(
+            user_id=1, task_id=42, reason="task_closed",
+        )
+
+    mock_create_task.assert_not_called()
+
+
+async def test_maybe_consolidate_unknown_reason_is_noop():
+    """Unknown reasons get logged and skipped — not raised."""
+    from fabledassistant.services import consolidation
+
+    with patch.object(
+        consolidation, "_logs_since_last_consolidation",
+        new=AsyncMock(return_value=99),
+    ), patch.object(
+        consolidation, "_auto_consolidate_enabled", new=AsyncMock(return_value=True),
+    ), patch(
+        "fabledassistant.services.consolidation.asyncio.create_task",
+    ) as mock_create_task:
+        await consolidation.maybe_consolidate(
+            user_id=1, task_id=42, reason="some_other_reason",
+        )
+
+    mock_create_task.assert_not_called()