MP match forensics: per-peer matchlog + relay auto-upload + matchcheck

For the 8-player playtest.  Damage authority is VICTIM-side, so no single
peer sees the whole match: every -net instance now writes a compact
machine-parseable matchlog_<date>_<time>_<pid>.txt (auto-armed by -net;
BT_MATCHLOG=1/0 overrides; solo silent), and at mission end a relay-mode
pod dials the relay game port (the seat-request throwaway-dial pattern,
envelope route -9) and streams the file back -- the relay saves every
peer's copy under matchlogs/ on the operator's machine, so testers send
nothing by hand.  tools/matchcheck.py <dir> reconciles all of them:
damage claimed (FIRE/PROJ/SPLASH/RAM, shooter-side) vs applied (DMG,
victim-side authoritative), kill/death replication across observers,
PLAYER_DEAD counts, scores, version skew, replicant-application and
unattributed-damage anomalies, mid-mission disconnects.

Hooks at the authoritative sites: Mech::TakeDamageMessageHandler (DMG,
post-base, zone + post-application damageLevel), MechWeapon::
SendDamageMessage (FIRE), projectile impact/splash/collision dispatch
(PROJ/SPLASH/RAM), wreck entry (DEATH -- a ONE-SHOT latch at
MovementMode 9, NOT the transition: a replicant arrives at 9 straight
from the type-6 record header and never runs the transition branch),
BTPlayer vehicle/death/score handlers (VEHICLE/PLAYER_DEAD/SCORE), zone
crit cascade (CRIT), APP.cpp RunningMission (MISSION), L4NET host
handlers (PEER_UP/PEER_DOWN).  Every line t=/w=/st=-stamped + fflushed.

Verified 2-node: mesh run pairs A's 22 FIRE 1:1 with B's 22 DMG (same
amounts, cylinder-resolved zones, ~200ms latency); force-damage kill run
logs 103 DMG + 3 DEATH inst=M + 3 PLAYER_DEAD across three respawn
cycles victim-side and the kill SCOREs shooter-side; relay-mode run
auto-uploaded BOTH peers' files at the mission-clock stop and matchcheck
produced the full report with exactly one (correct) anomaly -- the force
hook's claim-less damage, the unattributed-damage detector working.
Relay gained a route-specific 8MB cap for the upload frame (game frames
stay capped at 1600).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

game/reconstructed/matchlog.cpp

@@ -0,0 +1,142 @@
+//===========================================================================//
+// matchlog.cpp -- per-peer MP forensic combat log (PORT tooling, 2026-07-22)//
+//---------------------------------------------------------------------------//
+// See matchlog.hpp for the contract + event catalogue.  This TU only owns
+// the file + the line writer; the event call sites live at the authoritative
+// combat hooks (mech.cpp DMG, mechweap.cpp FIRE, mech4.cpp DEATH/PROJ/
+// SPLASH/RAM, btplayer.cpp VEHICLE/PLAYER_DEAD/SCORE, mechdmg.cpp CRIT) and
+// two engine seams (APP.cpp MISSION, L4NET.CPP PEER_UP/DOWN via extern).
+//===========================================================================//
+
+#include <bt.hpp>
+#include <app.hpp>				// Application/application (the st= line prefix)
+#include <matchlog.hpp>
+#include <btversion.h>
+
+#include <stdio.h>
+#include <stdarg.h>
+
+int
+	BTMatchHostOf(const EntityID &id)
+{
+	EntityID copy(id);						// GetHostID() is non-const
+	return (int)copy.GetHostID();
+}
+
+int
+	BTMatchLocalOf(const EntityID &id)
+{
+	return (int)id;							// operator int() const == localID
+}
+
+static FILE	*s_matchLog   = 0;
+static int	 s_matchState = -1;			// -1 unresolved, 0 off, 1 armed
+static char	 s_matchPath[160] = "";
+
+const char *
+	BTMatchLogPath()
+{
+	return s_matchPath;
+}
+
+void
+	BTMatchLogClose()
+{
+	if (s_matchLog != 0)
+	{
+		fflush(s_matchLog);
+		fclose(s_matchLog);
+		s_matchLog   = 0;
+		s_matchState = 0;				// further events: no-op
+	}
+}
+
+int
+	BTMatchLogActive()
+{
+	if (s_matchState >= 0)
+		return s_matchState;
+
+	//
+	// Resolve the gate once.  BT_MATCHLOG overrides; the default arms for
+	// any "-net" launch (every MP path) and stays silent for solo.
+	//
+	int on;
+	const char *e = getenv("BT_MATCHLOG");
+	if (e != 0)
+	{
+		on = (atoi(e) != 0);
+	}
+	else
+	{
+		const char *cmd = GetCommandLineA();
+		on = (cmd != 0 && strstr(cmd, "-net") != 0);
+	}
+
+	if (on)
+	{
+		SYSTEMTIME now;
+		GetLocalTime(&now);
+
+		sprintf(s_matchPath, "matchlog_%04u%02u%02u_%02u%02u%02u_%lu.txt",
+			(unsigned)now.wYear, (unsigned)now.wMonth, (unsigned)now.wDay,
+			(unsigned)now.wHour, (unsigned)now.wMinute, (unsigned)now.wSecond,
+			(unsigned long)GetCurrentProcessId());
+		s_matchLog = fopen(s_matchPath, "w");
+		if (s_matchLog == 0)
+			s_matchPath[0] = '\0';
+	}
+	s_matchState = (s_matchLog != 0) ? 1 : 0;
+
+	if (s_matchState)
+	{
+		char machine[MAX_COMPUTERNAME_LENGTH + 1] = "?";
+		DWORD machine_length = sizeof(machine);
+		GetComputerNameA(machine, &machine_length);
+
+		const char *self  = getenv("BT_SELF");
+		const char *relay = getenv("BT_RELAY");
+		SYSTEMTIME now;
+		GetLocalTime(&now);
+		BTMatchLog("HDR",
+			"ver=\"%s\" date=%04u-%02u-%02u pid=%lu machine=\"%s\" "
+			"self=\"%s\" relay=\"%s\" cmd=\"%s\"",
+			BT_VERSION_FULL,
+			(unsigned)now.wYear, (unsigned)now.wMonth, (unsigned)now.wDay,
+			(unsigned long)GetCurrentProcessId(), machine,
+			self  != 0 ? self  : "",
+			relay != 0 ? relay : "",
+			GetCommandLineA() != 0 ? GetCommandLineA() : "");
+	}
+	return s_matchState;
+}
+
+void
+	BTMatchLog(const char *tag, const char *format, ...)
+{
+	if (!BTMatchLogActive())
+		return;
+
+	char body[640];
+	va_list args;
+	va_start(args, format);
+	_vsnprintf(body, sizeof(body) - 1, format, args);
+	body[sizeof(body) - 1] = 0;
+	va_end(args);
+
+	SYSTEMTIME now;
+	GetLocalTime(&now);
+
+	// The app state rides every line (WaitingForEgg .. RunningMission ..)
+	// so the tool can window events to the live mission without a separate
+	// state-transition hook.
+	int app_state = (application != 0)
+		? (int)application->GetApplicationState() : -1;
+
+	fprintf(s_matchLog, "%s t=%lu w=%02u:%02u:%02u.%03u st=%d %s\n",
+		tag, (unsigned long)GetTickCount(),
+		(unsigned)now.wHour, (unsigned)now.wMinute,
+		(unsigned)now.wSecond, (unsigned)now.wMilliseconds,
+		app_state, body);
+	fflush(s_matchLog);
+}