fix: pyright errors in test file, bump pyright floor to 1.1.411

- Remove unused `import dataclasses` and stray `die as real_die` import
- Replace lambda side_effect callbacks with list side_effect; lambdas
  with untyped parameters trigger reportUnknownLambdaType in pyright
  >=1.1.400 — side_effect=[...] is both cleaner and type-safe
- Bump pyright floor from >=1.1.300 to >=1.1.411 in requirements-dev.txt
  so CI installs a version that matches what the lint job runs

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

requirements-dev.txt

@@ -3,5 +3,5 @@
 # These tools are used for code quality checks in CI/CD.
 
 pylint>=3.0.0
-pyright>=1.1.300
+pyright>=1.1.411
 coverage>=7.0.0