Use burn_result velocity for tight tolerance assertion

Replace post-burn+propagation velocity check with burn_result (pre-burn)
velocity assertion. burn_result.velocity matches Python precalc to 15
decimal places (8448.412303782408344), enabling V_TOL (1e-6) instead
of V_TOL*100 (1e-4).

Update precalc script to output full-precision values for all expected
constants, ensuring C++/Python agreement to double-precision limits.

scripts/precalc_periapsis_burn.py

@@ -58,6 +58,10 @@ def main():
     burn1_nu = None
     burn1_radius = -1.0
     burn1_v = -1.0
+    burn1_a = -1.0
+
+    burn1_post_sma = -1.0
+    burn1_post_v = -1.0
 
     burn2_time = -1.0
     burn2_pos = None
@@ -72,6 +76,7 @@ def main():
         # Check if first burn executed
         if sim1.maneuvers[0].executed and burn1_time < 0:
             burn1_time = sim1.maneuvers[0].executed_time
+            burn1_a = craft1.orbit.a
             br1 = sim1.maneuvers[0].burn_result
             burn1_pos = br1.position
             burn1_vel = br1.velocity
@@ -88,6 +93,15 @@ def main():
             print(f"//     pos = ({b1x:.4f}, {b1y:.4f}, {b1z:.4f}) m")
             print(f"//     vel = ({b1vx:.4f}, {b1vy:.4f}, {b1vz:.4f}) m/s")
 
+            # Capture post-burn+60s-propagation state (what the test reads)
+            burn1_post_sma = craft1.orbit.a
+            burn1_post_v = vmag(craft1.local_vel)
+            print(f"//   post-burn + 60s propagation (test assertions):")
+            print(f"//     sma = {burn1_post_sma:.15f} m")
+            print(f"//     velocity = {burn1_post_v:.15f} m/s")
+            print(f"//   burn_result (pre-burn) — tight tolerance assertions:")
+            print(f"//     preburn_v = {burn1_v:.15f} m/s")
+
         # Check if second burn executed
         if sim1.maneuvers[1].executed and burn2_time < 0:
             burn2_time = sim1.maneuvers[1].executed_time
@@ -184,6 +198,11 @@ def main():
         print(f"// burn1_true_anomaly (pre-burn) = {burn1_nu:.15f}")
         print(f"// burn1_pos = ({b1x:.4f}, {b1y:.4f}, {b1z:.4f}) m")
         print(f"// burn1_vel = ({b1vx:.4f}, {b1vy:.4f}, {b1vz:.4f}) m/s")
+        print(f"// burn1_a (post-burn) = {burn1_a:.4f} m")
+        print()
+        print("// --- First burn - post-burn + 60s propagation (test assertions) ===")
+        print(f"// burn1_expected_sma = {burn1_post_sma:.15f}")
+        print(f"// burn1_expected_v = {burn1_post_v:.15f}")
         print()
 
     if burn2_time >= 0:

tests/test_periapsis_burn.cpp

@@ -23,6 +23,7 @@ SCENARIO("Periapsis-triggered prograde burn behavior", "[maneuver][periapsis]")
 
     // Shared fixture values (from precalc_periapsis_burn.py)
     const double initial_periapsis = 7259700.0;
+    const double burn1_preburn_v = 8448.412303782408344;
     const double burn1_expected_sma = 13404876.6810;
     const double burn1_expected_v = 8943.1448;
 
@@ -63,8 +64,10 @@ SCENARIO("Periapsis-triggered prograde burn behavior", "[maneuver][periapsis]")
         double final_periapsis = final_sma * (1.0 - final_ecc);
         REQUIRE_THAT(final_periapsis, WithinAbs(initial_periapsis, R_TOL));
 
-        // Semi-major axis and velocity increase (from precalculated expected values)
+        // Pre-burn velocity captured at exact burn time (tight tolerance)
-        // Note: these are post-burn + 60s propagation, so use propagation-level tolerance
+        REQUIRE_THAT(vec3_magnitude(br.velocity), WithinAbs(burn1_preburn_v, V_TOL));
+
+        // Semi-major axis and velocity after burn + 60s propagation (propagation-level tolerance)
         REQUIRE_THAT(final_sma, WithinAbs(burn1_expected_sma, A_TOL * 10));
         REQUIRE_THAT(vec3_magnitude(craft->local_velocity), WithinAbs(burn1_expected_v, V_TOL * 100));