Phase A: Extend sim_engine.py with maneuver trigger detection
- Add TriggerType enum, Maneuver dataclass
- Implement check_maneuver_trigger() matching C++ sub-step logic
- Integrate maneuver execution into update_spacecraft()
- Add maneuvers_from_config() for TOML parsing
- Create precalc_periapsis_burn.py for expected value generation
Phase B: Refactor test_periapsis_burn.cpp
- Merge 4 TEST_CASEs into 1 SCENARIO with 5 SECTIONs
- Shared fixture setup in SCENARIO body
- Replace Approx() with WithinAbs() using named tolerance constants
- Use precalculated expected values for quantitative assertions
- Integer comparisons use REQUIRE() not WithinAbs()
- Add BurnResult plan comment for future burn-time state capture
TOML config converted to TOML 1.0 inline table syntax.