files: Ham Share's player — Auto quality, any by hand, or the file; 360 view; Transcode device setting

Every video plays YouTube's way: hls.js reads the connection and picks the
quality, or one is picked by hand, or Original plays the file as it is. The
qualities (a ladder by size, H.264) are made on the fly in 3 s pieces from
wherever the viewer seeks, one ffmpeg per play, paused when far enough ahead.
360 videos open in a look-around view (drag, pinch or scroll to zoom from
8 to 300 degrees, phone motion).

Settings -> Transcode device picks the machine and device that makes them,
for every machine's files: a machine transcoding another's file reads it
through the hub by a token for that one file. Replaces the codec/size picker
and the single-quality re-encoder.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/store/store.go

@@ -75,6 +75,16 @@ type State struct {
 	KVMCookies map[string]map[string]string `json:"kvm_cookies,omitempty"`
 	SamplerMs  int                          `json:"sampler_ms,omitempty"`  // how often this machine samples; the hub keeps every machine on the console's refresh rate
 	HistorySec int                          `json:"history_sec,omitempty"` // how far back the graphs reach; the hub keeps every machine on the same one
+	// Transcode is where videos played in the Files viewer are made (internal/api/play.go):
+	// a machine and a device on it. nil is the machine the file is on, its best device.
+	Transcode *Transcode `json:"transcode,omitempty"`
+}
+
+// Transcode names a device on a machine: Node "" is the hub itself; Device is a render node
+// or "cpu".
+type Transcode struct {
+	Node   string `json:"node"`
+	Device string `json:"device"`
 }
 
 // UserState returns the prefs of an account, making an empty one if needed.