[client] display: use trusted nominal cadence

Always track Wayland surface outputs alongside fractional scaling and use
RandR modes for X11 cadence. Remove render-derived feedback so a
throttled client cannot teach the producer to remain throttled.

Release scheduling after nominal output timing remains unavailable.

client/src/main.c

@@ -727,7 +727,6 @@ static int renderThread(void * unused)
     const uint64_t delta = t - g_state.lastRenderTime;
 
     g_state.lastRenderTime = t;
-    frameScheduler_observeRender(t);
     atomic_fetch_add_explicit(&g_state.renderCount, 1, memory_order_relaxed);
 
     if (!g_state.jitRender && g_params.fpsMin != 0)