fix(ui): show correct P2P Direct / Via Relay badge

The UI looked for event "connect:dual_path_race_won" which doesn't
exist — the actual event is "connect:path_negotiated" with a
use_direct boolean. Badge always showed "Via Relay" even when the
call was direct P2P.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

desktop/src/main.ts

@@ -1015,10 +1015,10 @@ async function pollStatus() {
     if (directCallPeer) {
       // Check the debug buffer for the race result to label
       // the connection type (P2P Direct vs Relay).
-      const raceWon = callDebugBuffer.find((e) => e.step === "connect:dual_path_race_won");
+      const pathNeg = callDebugBuffer.find((e) => e.step === "connect:path_negotiated");
       const engineOk = callDebugBuffer.find((e) => e.step === "connect:call_engine_started");
       if (engineOk) {
-        if (raceWon?.details?.path === "Direct") {
+        if (pathNeg?.details?.use_direct === true) {
           dcBadge.textContent = "P2P Direct";
           dcBadge.className = "dc-badge";
         } else {