test(ocr): assert ocr_jobs_total label is engine=surya for typewriter

Locks down AC2 for the non-Kurrent path. The same code branch in /ocr that
sets engine_name from script_type now has explicit coverage for both
HANDWRITING_KURRENT → kraken and TYPEWRITER → surya.

Refs #652 (AC2)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ocr-service/test_metrics.py

@@ -129,3 +129,29 @@ async def test_ocr_jobs_total_incremented_with_kraken_engine_label_for_kurrent(f
         engine="kraken", script_type="HANDWRITING_KURRENT"
     )._value.get()
     assert value == 1.0
+
+
+@pytest.mark.asyncio
+async def test_ocr_jobs_total_incremented_with_surya_engine_label_for_typewriter(fresh_metrics):
+    """A /ocr call with TYPEWRITER increments engine=surya."""
+    mock_images = [Image.new("RGB", (100, 100))]
+    mock_blocks = [{"pageNumber": 1, "x": 0.0, "y": 0.0, "width": 1.0, "height": 1.0,
+                    "polygon": None, "text": "hi", "words": []}]
+
+    with patch("main.kraken_engine.load_models"), \
+         patch("main.load_spell_checker"), \
+         patch("main._download_and_convert_pdf", new_callable=AsyncMock, return_value=mock_images), \
+         patch("main.preprocess_page", side_effect=lambda img: img), \
+         patch("main.surya_engine.extract_blocks", return_value=mock_blocks):
+        async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as client:
+            import main as main_module
+            main_module._models_ready = True
+            try:
+                await _drive_ocr(client, script_type="TYPEWRITER")
+            finally:
+                main_module._models_ready = False
+
+    value = fresh_metrics.ocr_jobs_total.labels(
+        engine="surya", script_type="TYPEWRITER"
+    )._value.get()
+    assert value == 1.0