Add "share status" command and a relay-piped fallback for cross-network peers

status: swarm.Client.Status()/RoomStatus/FileStatus report per-room peer
count and per-file chunk progress; daemon gets a "status" control action;
CLI gets "share status" to display it.

Relay fallback: peers advertising a LAN-only address can't be dialed
directly by peers on a different network. connectToPeer now races a
direct dial against a relay-piped connection (both sides derive the same
pairing key from their two IDs, independent of who arrives first) and
uses whichever succeeds. The relay grows a second, on-demand path
alongside room membership: a "pipe" request pairs two connections on a
key and forwards raw bytes between them from then on, same as the
original relay's behavior before the rendezvous-only redesign, just now
triggered per-pair only when direct connection fails.

src/daemon/protocol.go

@@ -1,9 +1,11 @@
 package daemon
 
+import "github.com/tzgyn/share/src/swarm"
+
 // request/response are the only vocabulary spoken over the control
 // socket between a CLI invocation and the background daemon.
 type request struct {
-	Action string       `json:"action"` // "join" or "stop"
+	Action string       `json:"action"` // "join", "stop", or "status"
 	Join   *joinRequest `json:"join,omitempty"`
 }
 
@@ -20,6 +22,7 @@ type joinRequest struct {
 }
 
 type response struct {
-	OK    bool   `json:"ok"`
-	Error string `json:"error,omitempty"`
+	OK    bool               `json:"ok"`
+	Error string             `json:"error,omitempty"`
+	Rooms []swarm.RoomStatus `json:"rooms,omitempty"` // "status" only
 }