Add crash handler: write crashlog + minidump to the game folder

[tais]

Problem

The shipped build has no crash reporting. The __try/__except around the game (sgp.cpp) is behind ENABLE_EXCEPTION_HANDLING, which is never defined, so an unhandled exception just terminates the process with nothing written — player crash reports are unactionable.

What this adds

A top-level crash handler, installed as the very first thing in WinMain. On any crash it writes two files to the game folder:

• CrashLog_<pid>.txt — readable summary: build version, timestamp, exception type, faulting module + offset, read/write access-violation address, and a symbolic call stack (function + file:line when a .pdb is beside the exe, module+offset otherwise). Actionable without a debugger.
• CrashDump_<pid>.dmp — a minidump. Opened with the matching ja2.pdb in Visual Studio / WinDbg it gives the full symbolic stack, locals and all threads.

A message box tells the player which two files to attach when reporting.

Coverage

• SEH crashes (access violations, etc. — the common case) via SetUnhandledExceptionFilter.
• CRT-fatal paths that bypass SEH — pure-virtual call, invalid CRT parameter, and abort()/SIGABRT (where an unhandled std::terminate also lands) — routed through the same writer via RtlCaptureContext.

Notes

• Uses Dbghelp.lib (already linked); single file, no CMake change.
• Hardened after review: writes the minidump before touching DbgHelp symbols (so a corrupt/locked loader list can't cost us the dump); reentrancy-guarded and __try-wrapped so the handler can't re-crash the report; reserves stack via SetThreadStackGuarantee (loaded dynamically for XP-era headers) so it still runs on a stack-overflow crash.
• Writes to the game folder (matches the request); if that folder isn't writable the report is skipped (message box still shows). A %TEMP% fallback could be added later.
• Windows/MSVC project — reviewed for MSVC compile-ability + DbgHelp correctness; validated by the branch CI build.

🤖 Generated with Claude Code