feat: harmonize MCP tool + userinfo page to documents/chunks model

Extend the documents-vs-chunks split to the remaining status surfaces so all
three report consistently (Deck #195):

- nc_get_vector_sync_status MCP tool + VectorSyncStatusResponse: add
  indexed_documents (distinct) and indexed_chunks; keep indexed_count as a
  deprecated alias of indexed_chunks. Reuses count_indexed.
- userinfo HTML page (/app/vector-sync/status): show Indexed Documents AND
  Indexed Chunks rows; switch its count to count_indexed (which also excludes
  placeholder points — the old raw count included them).
- /api/v1/vector-sync/status: restore indexed_count as a deprecated alias of
  indexed_chunks so existing consumers (integration tests, pre-#115 UI) keep
  working; the change is now purely additive for indexed_count.

Tests: VectorSyncStatusResponse documents/chunks/alias + zeroed defaults.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/unit/test_vector_sync_status_model.py

@@ -0,0 +1,36 @@
+"""Unit tests for VectorSyncStatusResponse documents-vs-chunks fields."""
+
+import pytest
+
+from nextcloud_mcp_server.models.semantic import VectorSyncStatusResponse
+
+pytestmark = pytest.mark.unit
+
+
+def test_vector_sync_status_documents_and_chunks() -> None:
+    """Exposes documents AND chunks; indexed_count is a deprecated chunks alias."""
+    response = VectorSyncStatusResponse(
+        indexed_documents=486,
+        indexed_chunks=16039,
+        indexed_count=16039,  # deprecated alias
+        pending_count=2214,
+        status="syncing",
+        enabled=True,
+        ingest_queue="memory",
+    )
+
+    data = response.model_dump()
+    assert data["indexed_documents"] == 486
+    assert data["indexed_chunks"] == 16039
+    # Alias mirrors chunks (not documents) for back-compat.
+    assert data["indexed_count"] == data["indexed_chunks"]
+    assert data["pending_count"] == 2214
+
+
+def test_vector_sync_status_defaults_zeroed() -> None:
+    """New corpus fields default to 0 (disabled / pre-sync path)."""
+    response = VectorSyncStatusResponse(status="disabled", enabled=False)
+    data = response.model_dump()
+    assert data["indexed_documents"] == 0
+    assert data["indexed_chunks"] == 0
+    assert data["indexed_count"] == 0