Complements the inline-dict unit tests in test_config_validate.py with
10 real JSON config files under tests/utils/fixtures/ (valid sim/real/
Normal configs, one with legacy unknown keys that must NOT fail, and
six broken variants covering each distinct failure mode: missing gain,
missing Inner branch, missing pid_type, missing TempCtrl entirely,
wrong-typed gain, TempCtrl not a dict).
test_config_fixtures.py drives all of them from one CASES table
(fixture name -> expected pass/ConfigError-regex), plus a guard test
that fails if fixtures/ and CASES ever drift apart.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01F4oEE99rkKVU8L8tkzXWdG
