Initial commit — leak-hunt project complete

Five bugs identified and patched in retail Asheron's Call client:
- v3b: palette refcount over-increment (3-byte NOP at two sites)
- v5: RenderSurface PurgeResource no-op stub (vtable slot 2 thunk)
- v11: two dangling-pointer crash guards (NULL-check + reorder)
- v14: CEnvCell::Destroy ClipPlaneList leak (18-byte JMP to cleanup thunk)
- v22: unpacker stale-pointer SEH guard (whole-function __try/__except)

All five ship in leakfix.dll (117 KB, SHA d282f23c…) which is loaded
by acclient.exe at process start via PE import table patching by
tools/install_leakfix.py.

Controlled 15-client fleet soak: unpatched control died at 26h with
palette exhaustion; all 14 patched clients survived past that point
and reached ≥5-day uptime.

Residual ~15 MB/h growth traced to d3d9.dll's internal slab allocator
(260KB surface backing buffers retained after Release). See REPORT.md
§10 for the full investigation; conclusion is that it's unfixable from
outside d3d9.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dll/leakfix/stable/src.stable/instr.h

@@ -0,0 +1,19 @@
+// instr.h — instrumentation features for leakfix.dll
+#pragma once
+
+namespace leakfix {
+
+// Install SetUnhandledExceptionFilter so any unhandled native exception
+// writes a clean minidump to leakfix_crash_<pid>_<timestamp>.dmp next
+// to the DLL, then chains to Windows' default handling.
+void instr_install_crash_handler();
+
+// Start a background thread that scans memory every 5 minutes,
+// counts known leak-class vtable instances, and appends a one-line
+// summary to leakfix.log.
+void instr_start_periodic_scan();
+
+// Stop the periodic scan thread (called from DLL_PROCESS_DETACH).
+void instr_stop_periodic_scan();
+
+} // namespace leakfix