Net: Steam lobby (btl4lobby) + launch-mode wiring (Workstream C.2)

Port RP412's RPL4LOBBY to BT: an ISteamMatchmaking room stands in for the
arcade Site-Management screen. Compiled both gates -- stubs without
BT412_STEAM, the full room under it (both configs build + link clean).

Lobby (game/reconstructed/btl4lobby.*):
- Room screen (green-on-black, like the menu), owner = console.
- Member data: FakeIP + fake console/game ports + persona + mech/color/badge
  (ip/cp/gp/nm/vh/cl/bd keys).
- Nonced "go" launch roster -> SteamNetTransport_RegisterPeer for every peer.
- Push/PullRaceResults over lobby data rebuild the shared score sheet.

Front end (btl4fe.*): HOST/JOIN buttons when BTLobby_Available() (Steam
transport up); the menu loop exits on a steam action and BTFrontEnd_Run
routes the lobby outcome -- host builds the egg with every member as a
[pilots] mesh entry (BTFrontEnd_SetHostedPilots), member returns launch
mode 2. Results screen prefers the marshal's collated result names.

Marshal (btl4console.*): add GetResultName / ClearResults / InjectResult so
the lobby owner can refill the sheet from the collated wire scores; Result
gains a name field.

WinMain (btl4main.cpp): install the Steam transport on BT412STEAM env
(before the front end, so the lobby is offered); branch on
BTFrontEnd_LastLaunchMode() -- host owns the marshal clock + joins the mesh,
member enters as a network pod on :1501 (SetNetworkCommonFlatAddress +
gConsoleLossEndsMission); Push (host) / Pull (member) results, then relaunch.

CMake: btl4lobby.cpp joins bt410_l4; that lib gets BT412_STEAM + the
Steamworks include under the gate. build-steam/ gitignored.

Deferred (untestable here -- needs Steam + multiple machines): the
host->member wire egg-feed marshal (InstallNetworkRace); a member currently
waits for a console connection nothing supplies, so a live host+member race
is blocked on it. The lobby object does not survive the per-mission
relaunch. docs/STEAM-3-MACHINE-TEST.md for BT not yet authored.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

game/reconstructed/btl4console.cpp

@@ -9,6 +9,8 @@
 #include <bt.hpp>				// Application, application, DEBUG_STREAM
 #pragma hdrstop
 
+#include <string.h>				// strncpy (result names from the wire)
+
 #include "appmsg.hpp"			// full Application::StopMissionMessage definition
 #include "appmgr.hpp"			// gPerFrameHook
 #include "btl4console.hpp"
@@ -31,7 +33,7 @@ namespace
 
 	// Final scores snapshotted at the stop (roster order; slot 0 = local).
 	enum { maxResults = 8 };
-	struct Result { int kills, deaths; };
+	struct Result { int kills, deaths; char name[24]; };
 	Result gResults[maxResults];
 	int    gResultCount = 0;
 
@@ -45,6 +47,7 @@ namespace
 				break;						// past the last occupied roster slot
 			gResults[gResultCount].kills  = BTPilotKills(pilot);
 			gResults[gResultCount].deaths = BTPilotDeaths(pilot);
+			gResults[gResultCount].name[0] = 0;		// filled by the lobby (owner) if networked
 			++gResultCount;
 		}
 		DEBUG_STREAM << "[marshal] snapshot " << gResultCount << " pilot score(s)\n" << std::flush;
@@ -136,6 +139,33 @@ int BTLocalConsole_GetResult(int index, int *kills, int *deaths)
 	return 1;
 }
 
+const char *BTLocalConsole_GetResultName(int index)
+{
+	if (index < 0 || index >= gResultCount)
+		return "";
+	return gResults[index].name;
+}
+
+// The lobby rebuilds the sheet from wire data (owner collates every pod's
+// scores) before showing the shared results, so it needs to clear + refill.
+void BTLocalConsole_ClearResults()
+{
+	gResultCount = 0;
+}
+
+void BTLocalConsole_InjectResult(int slot, int kills, int deaths, const char *name)
+{
+	if (slot < 0 || slot >= maxResults)
+		return;
+	gResults[slot].kills  = kills;
+	gResults[slot].deaths = deaths;
+	gResults[slot].name[0] = 0;
+	if (name) { strncpy(gResults[slot].name, name, sizeof(gResults[slot].name) - 1);
+		gResults[slot].name[sizeof(gResults[slot].name) - 1] = 0; }
+	if (slot >= gResultCount)
+		gResultCount = slot + 1;
+}
+
 void BTLocalConsole_Uninstall()
 {
 	gPerFrameHook = 0;