Smoother daemon: no-op reloads, batched placement, muted audio, graceful teardown

- Skip stream restarts when a reload resolves to the identical wall
  (same URLs, tile geometry, player settings) — saving an unrelated
  config edit no longer blanks the screen.
- Replace per-tile placement polling (a swaymsg fork per tile per second,
  plus 150ms get_tree polling per tile at startup) with one shared loop:
  a single get_tree snapshot per tick, re-placing only drifted windows,
  relaxing to a 2s tick once settled.
- Mute streams by default (--no-audio) to skip an audio decoder per
  stream; opt back in with player.audio: true.
- Graceful, parallel mpv teardown via cmd.Cancel/WaitDelay, fixing the
  double-Wait race between Stop and Supervise and cutting worst-case
  layout switches from ~2s x N streams to ~2s total.
- status: probe mpv IPC outside the daemon mutex so a slow probe can't
  block layout switches.
- View sync: reuse the Protect session across ticks (re-login only on
  expiry) and pick up view_refresh_seconds changes without a restart.
- Health strikes keyed by player, not slot, so they never carry across
  layout switches; prune stale entries.
- New `rtsp-streamer reload` CLI; fix dead sort in `layout ls`; back off
  on persistent control-socket accept errors; fsync config before the
  atomic rename (SD-card power-cut safety); bump IPC client deadline;
  gofmt stragglers.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/config/config.go

@@ -88,6 +88,10 @@ type Player struct {
 	// MaxFPS caps the rendered frame rate (mpv --vf=fps). 0 = uncapped. Trims
 	// render/scale load; the bigger decode lever is using substreams.
 	MaxFPS int `yaml:"max_fps,omitempty"`
+	// Audio enables stream sound. Off by default: a wall of simultaneous
+	// feeds is unwatchable with sound, and skipping the audio decoder saves
+	// CPU per stream.
+	Audio bool `yaml:"audio,omitempty"`
 	// RestartBackoffSeconds is how long to wait before relaunching a stream
 	// that exited or stalled.
 	RestartBackoffSeconds int `yaml:"restart_backoff_seconds,omitempty"`
@@ -436,6 +440,12 @@ func Save(path string, c *Config) error {
 		tmp.Close()
 		return err
 	}
+	// Flush to stable storage before the rename: on SD cards a power cut
+	// between rename and writeback can otherwise leave an empty config.
+	if err := tmp.Sync(); err != nil {
+		tmp.Close()
+		return err
+	}
 	if err := tmp.Close(); err != nil {
 		return err
 	}