fix(programmer): day rows — Delta JSON test + non-assignee row gate

- Add Delta JSON happy-path test case to deltaJsonToPlainText tests
- Fix double-row bug: notes-only assignee rows only when userId == assigneeId
- Remove dead code: tautological taskMap.containsKey check in loop
Co-Authored-By: claude-flow <ruv@ruv.net>

test/programmer_day_rows_test.dart

@@ -24,6 +24,10 @@ void main() {
       expect(deltaJsonToPlainText('[{invalid json'), '[{invalid json');
     });
 
+    test('Delta JSON with insert is converted to plain text', () {
+      expect(deltaJsonToPlainText('[{"insert":"Hello\\n"}]'), 'Hello');
+    });
+
     test('Delta JSON arrays starting with [ are attempted to be parsed', () {
       // The function attempts to parse JSON that starts with '['
       // If parsing fails, it returns the trimmed string