Extract query page rendering into new QueryPage module

Refactor QueryView.get() by moving query execution, CSV streaming,
renderer dispatch, and HTML template rendering into a new
datasette/query_page.py module. Share renderer dispatch logic between
query and table views via dispatch_renderer(). Fix query view passing
view_name="query" instead of "table" to output renderers.

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

tests/test_plugins.py

@@ -502,6 +502,19 @@ async def test_hook_register_output_renderer_all_parameters(ds_client):
     }
 
 
+@pytest.mark.asyncio
+async def test_hook_register_output_renderer_query_view_name(ds_client):
+    response = await ds_client.get(
+        "/fixtures/-/query.testall?sql=select+1"
+    )
+    assert response.status_code == 200
+    body = at_memory_re.sub(" at 0xXXX", response.text)
+    data = json.loads(body)
+    assert data["view_name"] == "query"
+    assert data["table"] is None
+    assert data["database"] == "fixtures"
+
+
 @pytest.mark.asyncio
 async def test_hook_register_output_renderer_custom_status_code(ds_client):
     response = await ds_client.get(