document '{}' instead of '{0}' for zero initialization

AGENTS.md

@@ -21,7 +21,7 @@
 - No trailing whitespace in any files (including markdown)
   - Pre-commit hook automatically strips it
   - For markdown line breaks, use <br> tag instead of two trailing spaces
-- ZII (Zero Is Initialization) pattern: Initialize structs using `= {0}` or `= {NULL}` instead of individual field assignments. This guarantees all fields (including padding) are zeroed out. Example: `MyStruct s = {0};`
+- ZII (Zero Is Initialization) pattern: Initialize structs using `type_name s = {};`
 
 ## File Reading Policy
 - Ask before reading files unless immediately necessary for current task

tests/test_true_anomaly_roundtrip.cpp

@@ -11,7 +11,7 @@ SCENARIO("True anomaly round-trip conversion and radius sanity checks",
     const double parent_mass = 5.972e24;
     const double a = 7000e3;
     const double e = 0.3;
-    OrbitalElements elements = {0};
+    OrbitalElements elements = {};
     elements.semi_major_axis = a;
     elements.eccentricity = e;
     Vec3 pos, vel;