common: take ROIAzimuthal phi as plain floats, not optionals

The phi bounds were stored as plain floats internally but passed through
std::optional in the constructor, which obscured the intent. Take them
as float arguments defaulting to 0 instead. The convention is explicit:
phi_min == phi_max means the full ring (all angles), a sector wraps
across 0 when phi_min > phi_max, and otherwise phi_min <= phi_max. The
"both bounds or none" rule belongs at the API/file boundary
(OpenAPIConvert, reader), not in the core class, so it lives there now.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/ROIMapTest.cpp

@@ -226,9 +226,11 @@ TEST_CASE("ROIAzimuthal_Phi_Normalize", "[ROIMap]") {
     REQUIRE(sector.GetPhiMin_deg() == 330.0f);
     REQUIRE(sector.GetPhiMax_deg() == 40.0f);
 
-    // Only one phi bound provided -> treated as full ring
-    ROIAzimuthal one_bound("roi2", 2.0, 4.0, 30.0f);
-    REQUIRE_FALSE(one_bound.HasPhi());
+    // Default (no phi bounds) and equal bounds are both the full ring
+    ROIAzimuthal full("roi2", 2.0, 4.0);
+    REQUIRE_FALSE(full.HasPhi());
+    ROIAzimuthal equal_bounds("roi3", 2.0, 4.0, 45.0f, 45.0f);
+    REQUIRE_FALSE(equal_bounds.HasPhi());
 }
 
 TEST_CASE("ROIAzimuthal_Phi_MarkROI", "[ROIMap]") {