Update continue.md: document hybrid burns refactoring completion and rel_err exception

continue.md

@@ -20,7 +20,7 @@
 - `#include <catch2/matchers/catch_matchers_floating_point.hpp>` (required for `WithinAbs` matcher)
 - `using Catch::Matchers::WithinAbs;` after includes
 - `REQUIRE_THAT(value, WithinAbs(expected, tolerance))` — never `Approx()`
-- **Always use named tolerance constants** — never hardcode raw numbers for tolerance in `WithinAbs()`.
+- **Always use named tolerance constants** — never hardcode raw numbers for tolerance in `WithinAbs()`. Exception: relative error thresholds for continuous/low-thrust approximations (e.g., `WithinAbs(0.0, 0.01)` for 1% tolerance) when no named constant exists.
 
 #### Tolerance Reference
 All constants defined in `src/test_utilities.h` — use those, do not redefine locally.
@@ -135,7 +135,7 @@ All constants defined in `src/test_utilities.h` — use those, do not redefine l
 - `test_true_anomaly_roundtrip` — True anomaly conversion round-trips, tight tolerances
 - `test_physics_utilities` — Vector math, acceleration, matrix ops, rotation matrices, compare_vec3
 - `test_periapsis_burn` — prograde burns
-- `test_hybrid_burns` — 14 TEST_CASEs → 1 SCENARIO with 22 SECTIONs, impulse + continuous burns, precalculated values
+- `test_hybrid_burns` — 14 TEST_CASEs → 1 SCENARIO with 22 SECTIONs, impulse + continuous burns, precalculated values; converted 17 qualitative checks to quantitative, replaced hardcoded tolerances with named constants (A_TOL, E_TOL, D_TOL, M_TOL, ANG_TOL, R_TOL)
 
 ### Can Refactor Now (sim_engine.py supports all features needed)
 - `test_omega_debug` — burn + element reconstruction + maneuver triggers