3 surgical fixes:
1. src/openai_schemas.py: add custom __init__ to NormalizedResponse
that accepts BOTH the new nested usage: UsageStats AND the legacy
flat usage_input_tokens=... kwargs. Fixes 12 of the 14 failing tests
in one place (no test changes needed).
2. tests/test_auto_whitelist.py: use dataclasses.replace() instead of
mutating a frozen Session via dict assignment.
3. tests/test_command_palette_sim.py: use a deterministic close callback
(or push toggle twice as fallback) instead of the non-deterministic
_toggle_command_palette callback.
4 phases, 4 tasks, 6 atomic commits expected. Verification: full
scripts/run_tests_batched.py is green; 4 audit gates remain clean;
no new failures introduced.
ed