Place windows at map time so stream restarts never flash

Diagnosis: individual tiles flickered when their stream died and mpv
relaunched (confirmed via status: a PID dropping to 0 and coming back).
The restarted window mapped at the video's native size wherever sway
dropped it, and the corrective loop only snapped it into its cell on the
next tick — up to 2s later on the relaxed cadence.

Fix, at the source instead of racing the map:
- Pre-install a per-slot for_window rule (matched on each mpv's unique
  window title, anchored so slot-1 never matches slot-10) so sway
  positions and sizes the window synchronously the moment it maps.
- Pass --geometry=WxH per tile so mpv opens at the tile size rather
  than resizing itself to the video's native size on load.

The placeLoop remains as a corrective backstop for mid-life drift.

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

internal/daemon/daemon.go

@@ -177,6 +177,13 @@ func (d *Daemon) applyLayout(ctx context.Context, name string) error {
 
 	for _, s := range specs {
 		p := player.New(s.slot, s.name, s.url, cfg.Player, d.runDir, d.log)
+		p.TileW, p.TileH = s.rect.W, s.rect.H
+		// Pre-install the placement rule so sway positions this slot's window
+		// (including after mid-life mpv restarts) the moment it maps — no
+		// wrong-place flash while waiting for the corrective loop.
+		if err := d.comp.PlaceOnMap(ctx, p.Title(), s.rect); err != nil {
+			d.log.Warn("could not preinstall placement rule", "slot", s.slot, "err", err)
+		}
 		players = append(players, p)
 		places = append(places, placement{p: p, rect: s.rect})