Add lightweight crash handler for pre-Sentry startup backtraces (#853)

- Install a crash handler at the very top of main() in both zenserver and zen
- On Windows, uses SetUnhandledExceptionFilter with StackWalk64 for accurate
  crash-site backtraces with DbgHelp symbol resolution
- On Linux/Mac, uses sigaction with async-signal-safe backtrace output
- Automatically superseded when Sentry/crashpad installs its own handlers
- Stays active for the full process lifetime if Sentry is disabled or absent
- Include .sym debug symbol files in Linux release bundle

1 files changed, 19 insertions, 0 deletions

diff --git a/src/zencore/include/zencore/crashhandler.h b/src/zencore/include/zencore/crashhandler.h
new file mode 100644
index 000000000..bfb5c740e
--- /dev/null
+++ b/src/zencore/include/zencore/crashhandler.h
@@ -0,0 +1,19 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#pragma once
+
+#include <zencore/zencore.h>
+
+namespace zen {
+
+/// Install a lightweight crash handler that prints backtraces to stderr.
+///
+/// Call as early as possible in main(). On Windows, uses SetUnhandledExceptionFilter;
+/// on Linux/Mac, installs signal handlers for SIGSEGV, SIGABRT, SIGFPE, SIGBUS, SIGILL.
+///
+/// The handler is automatically superseded when a crash reporter such as Sentry
+/// installs its own handlers. If no crash reporter is installed, this handler
+/// remains active for the lifetime of the process.
+void InstallCrashHandler();
+
+}  // namespace zen