test: add offline unit tests for Phase A reliability fixes

Mock-based tests (no live services) covering:
- ollama_llm_model resolution under the OLLAMA_MODEL env collision
- per-leg retrieval failure -> source_status/degraded signaling
- Phase 0/Phase 4 LLM timeout fallbacks
- /stats wiki page count using the users/{user} path prefix
- Wiki.js list_all_pages limit-growth pagination and
  list_pages limit-after-filter behavior

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_stats.py

@@ -0,0 +1,99 @@
+"""
+Unit tests for the /stats endpoint (offline, all clients mocked).
+
+Covers the wiki page count fix: the endpoint must count pages under the
+user namespace ("users/{user}"), not pass the bare user name as prefix
+(which matched nothing and always reported 0 pages).
+"""
+
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from src.main import stats
+
+
+@pytest.fixture
+def neo4j_client():
+    neo4j = MagicMock()
+    neo4j.execute_query = AsyncMock(return_value=[{"count": 5}])
+    return neo4j
+
+
+@pytest.fixture
+def qdrant_client():
+    qdrant = MagicMock()
+    qdrant.list_collections = AsyncMock(return_value=[
+        {"name": "user_jp", "vectors_count": 42}
+    ])
+    return qdrant
+
+
+@pytest.fixture
+def wikijs_client():
+    wikijs = MagicMock()
+    wikijs.list_all_pages = AsyncMock(return_value=[
+        {"id": i, "path": f"users/jpmschweitzer/p{i}"} for i in range(138)
+    ])
+    return wikijs
+
+
+@pytest.fixture
+def paperless_client():
+    paperless = MagicMock()
+    paperless.list_documents = AsyncMock(return_value={"count": 3})
+    paperless.list_tags = AsyncMock(return_value=[])
+    paperless.list_correspondents = AsyncMock(return_value=[])
+    paperless.list_document_types = AsyncMock(return_value=[])
+    return paperless
+
+
+@pytest.mark.unit
+class TestStatsWikiPageCount:
+    """/stats must scope the wiki page count to the user namespace."""
+
+    async def test_uses_user_namespace_path_prefix(
+        self, neo4j_client, qdrant_client, wikijs_client, paperless_client
+    ):
+        await stats(
+            user="jpmschweitzer",
+            neo4j=neo4j_client,
+            qdrant=qdrant_client,
+            wikijs=wikijs_client,
+            paperless=paperless_client,
+            api_key="test-key",
+        )
+
+        wikijs_client.list_all_pages.assert_awaited_once_with(
+            path_prefix="users/jpmschweitzer"
+        )
+
+    async def test_reports_page_count(
+        self, neo4j_client, qdrant_client, wikijs_client, paperless_client
+    ):
+        response = await stats(
+            user="jpmschweitzer",
+            neo4j=neo4j_client,
+            qdrant=qdrant_client,
+            wikijs=wikijs_client,
+            paperless=paperless_client,
+            api_key="test-key",
+        )
+
+        assert response.wiki_pages == 138
+
+    async def test_wiki_failure_degrades_to_zero(
+        self, neo4j_client, qdrant_client, wikijs_client, paperless_client
+    ):
+        wikijs_client.list_all_pages = AsyncMock(side_effect=RuntimeError("wiki down"))
+
+        response = await stats(
+            user="jpmschweitzer",
+            neo4j=neo4j_client,
+            qdrant=qdrant_client,
+            wikijs=wikijs_client,
+            paperless=paperless_client,
+            api_key="test-key",
+        )
+
+        assert response.wiki_pages == 0