fix: cv_init — replace memset with value-init to avoid UB on std::vector

Also fix stale path comment in test/test_cv/test_cv.cpp.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

firmware/lib/cv/cv.cpp

@@ -5,7 +5,7 @@
 #include <algorithm>
 
 void cv_init(CVState& state) {
-    memset(&state, 0, sizeof(CVState));
+    state = CVState{};   // value-initialize — calls vector default ctor correctly
     state.next_id = 1;
 }
 

firmware/test/test_cv/test_cv.cpp

@@ -1,4 +1,4 @@
-// firmware/test/test_native/test_cv.cpp
+// firmware/test/test_cv/test_cv.cpp
 #include <unity.h>
 #include <string.h>
 #include "cv.h"