test(vector): unit-test page-aware routing; clarify fallback comment

Address claude-review round 2 on PR #868:
- Extract the use_page_aware branching into a pure `should_use_page_aware`
  helper and cover the (doc_type, page_boundaries, page_aware_setting) matrix
  in tests/unit/test_processor_routing.py (file+boundaries+enabled, empty
  list, None, non-file doc types, disabled setting).
- Clarify the PageAwareChunker.chunk_text no-boundaries comment: the processor
  pre-filters via should_use_page_aware, so that branch is a direct-call safety
  net, not a production indexing path.

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

tests/unit/test_processor_routing.py

@@ -0,0 +1,62 @@
+"""Unit tests for the page-aware chunker routing decision (processor.py)."""
+
+import pytest
+
+from nextcloud_mcp_server.vector.processor import should_use_page_aware
+
+pytestmark = pytest.mark.unit
+
+_BOUNDARIES = [{"page": 1, "start_offset": 0, "end_offset": 10}]
+
+
+class TestShouldUsePageAware:
+    """Cover the (doc_type, page_boundaries, page_aware_setting) matrix."""
+
+    def test_pdf_with_boundaries_and_enabled_uses_page_aware(self):
+        assert (
+            should_use_page_aware(
+                page_aware_enabled=True,
+                doc_type="file",
+                page_boundaries=_BOUNDARIES,
+            )
+            is True
+        )
+
+    def test_empty_boundaries_falls_back_to_char_based(self):
+        """Empty list carries no pages -> char-based path."""
+        assert (
+            should_use_page_aware(
+                page_aware_enabled=True, doc_type="file", page_boundaries=[]
+            )
+            is False
+        )
+
+    def test_none_boundaries_falls_back_to_char_based(self):
+        assert (
+            should_use_page_aware(
+                page_aware_enabled=True, doc_type="file", page_boundaries=None
+            )
+            is False
+        )
+
+    @pytest.mark.parametrize("doc_type", ["note", "deck_card", "news_item"])
+    def test_non_file_doc_types_never_page_aware(self, doc_type):
+        """Only paginated files are page-aware, even with boundaries present."""
+        assert (
+            should_use_page_aware(
+                page_aware_enabled=True,
+                doc_type=doc_type,
+                page_boundaries=_BOUNDARIES,
+            )
+            is False
+        )
+
+    def test_disabled_setting_forces_char_based(self):
+        assert (
+            should_use_page_aware(
+                page_aware_enabled=False,
+                doc_type="file",
+                page_boundaries=_BOUNDARIES,
+            )
+            is False
+        )