perf(mobile): lower StopClient join timeout from 3s to 1s and log slow shutdown

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When the user taps Disconnect, GooseRelayVpnService.stopVpn() waits up to 5 seconds (stopThread.join(5000L)) for Go's StopClient() to return. Inside StopClient(), after the carrier cancel() and SOCKS listener close, it waits another up to 3 seconds on <-clientDone. The inner 3s timeout is redundant with the outer 5s join.

On a healthy disconnect where the carrier shuts down in <200ms (the common case), the user still sees ~3s of "DISCONNECTING" + 500ms fade ≈ 3.5s, where the inner 3s timeout is the sole contributor — the outer 5s never kicks in.

Change: Lower the inner <-clientDone wait from 3s → 1s. If the carrier takes longer than 1s, log it and return — the outer 5s join still caps total disconnect at a sane value. Healthy disconnect drops from ~3.5s → ~1.5s with no behavioral regression.

The new [client] carrier shutdown exceeded 1s log line surfaces slow shutdowns for debugging without changing StopClient's gomobile API surface (which would ripple to Kotlin callers).

Files changed

• mobile/mobile.go — single block replacement (+9/-1)

CI gates to watch

• go vet (Linux — syscall.Dup resolves; the Windows-only vet error in dupFd is pre-existing, unrelated)
• AAR build (bash ./android/build_go_mobile.sh)
• ./gradlew :app:assembleDebug