Add native self-hosted instance connection to fluxer_desktop

Trimmed monorepo checkout (fluxer_desktop + packages/voice_engine_v2 +
tools/ci) with a "Connect to a Different Server" menu item and popout
that lets the desktop app switch to any self-hosted Fluxer instance,
plus fixes for well-known discovery on single-domain self-hosted
deployments and a false-positive ERR_ABORTED on same-origin client
redirects during the switch. Defaults to chat.fluxr.chat and uses an
isolated userData directory from the official build.

fluxer_desktop/native/rt-thread/benches/baseline.json

@@ -0,0 +1,24 @@
+{
+	"measured_at": "85e057a273fd",
+	"host": "darwin-arm64-apple-silicon",
+	"regression_budget_percent": 5.0,
+	"criterion_args": {
+		"warm_up_time_sec": 2,
+		"measurement_time_sec": 5
+	},
+	"benches": {
+		"tick_driver/audio_21_33ms": {
+			"median_ns": 21415000.0,
+			"low_ns": 21395000.0,
+			"high_ns": 21441000.0,
+			"note": "Measures real-time sleep precision against AUDIO_TICK_PERIOD_NS=21333333; baseline reflects clock+scheduler delay on this host, not pure CPU work."
+		},
+		"system_clock_now_ns": {
+			"median_ns": 22.931,
+			"low_ns": 22.763,
+			"high_ns": 23.099,
+			"budget_percent_override": 15.0,
+			"note": "23ns op; clock_gettime variance dominates over 5%. Wider budget reflects the floor of measurement noise."
+		}
+	}
+}

fluxer_desktop/native/rt-thread/benches/tick.rs

@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+use std::hint::black_box;
+use std::sync::Arc;
+
+use criterion::{Criterion, criterion_group, criterion_main};
+use fluxer_rt_thread::{MonotonicClock, SystemMonotonicClock, TickDriver};
+
+const AUDIO_TICK_PERIOD_NS: u64 = 21_333_333;
+
+fn bench_audio_tick(c: &mut Criterion) {
+    let mut group = c.benchmark_group("tick_driver");
+    group.sample_size(20);
+    group.bench_function("audio_21_33ms", |b| {
+        b.iter_custom(|iters| {
+            let clock = Arc::new(SystemMonotonicClock::new());
+            let mut driver = TickDriver::new(clock.clone(), AUDIO_TICK_PERIOD_NS).expect("driver");
+            let _ = driver.wait_until_next_tick().expect("warmup");
+            let start = std::time::Instant::now();
+            for _ in 0..iters {
+                let info = driver.wait_until_next_tick().expect("tick");
+                black_box(info);
+            }
+            start.elapsed()
+        })
+    });
+    group.finish();
+}
+
+fn bench_now_ns(c: &mut Criterion) {
+    let clock = SystemMonotonicClock::new();
+    c.bench_function("system_clock_now_ns", |b| {
+        b.iter(|| {
+            let v = MonotonicClock::now_ns(&clock);
+            black_box(v)
+        })
+    });
+}
+
+criterion_group!(benches, bench_audio_tick, bench_now_ns);
+criterion_main!(benches);