fix(valgrind): suppress libstdc++ static-init exception pool

ctest -T memcheck flagged "Defects: 1 (Potential Memory Leak)" on every
test binary — including HeapLogTest, which has no real memory defect
(ERROR SUMMARY: 0). The block is the 72,704-byte libstdc++ emergency
exception pool allocated once by eh_alloc.cc's static initializer and
intentionally never freed; with -static-libstdc++ the frame appears as
_GLOBAL__sub_I_eh_alloc.cc in the binary itself, so the existing
__cxa_get_globals suppression never matched.

Suppression stack captured with --gen-suppressions=all in the exact CI
environment (Ubuntu 22.04, clang-16, Valgrind 3.18 via the map2check-dev
Docker image). With it, the full 6-test ctest -T memcheck suite reports
0 defects and exits 0.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: hbgit

valgrind.supp

@@ -26,6 +26,19 @@
 }
 
 # --- libstdc++: pool de emergência para exceções (alocado uma vez, by design) ---
+# 72.704 bytes "still reachable" alocados pelo inicializador estático de
+# eh_alloc.cc; nunca liberados de propósito (usados para lançar bad_alloc
+# em OOM). O ctest -T memcheck conta como "Potential Memory Leak" sem esta
+# supressão. Stack verificado no ambiente do CI (Ubuntu 22.04, clang-16,
+# -static-libstdc++, Valgrind 3.18).
+{
+   libstdcpp-eh-pool-static-init
+   Memcheck:Leak
+   match-leak-kinds: reachable
+   fun:malloc
+   fun:_GLOBAL__sub_I_eh_alloc.cc
+}
+# Variante para libstdc++ linkada dinamicamente (mesmo pool, outro stack).
 {
    libstdcpp-eh-pool
    Memcheck:Leak