feat(go-services): tracker share_* handlers (complete ingest) + shadow tuning

- share.go: cross-machine vital sharing (share_subscribe/unsubscribe/share_*),
  faithful port of the peer-state snapshot + plugin fan-out + /vital-sharing/peers.
  The last ingest handler — the Go tracker now handles every plugin event type.
- shadow consumer: drop the outbound keepalive ping (the firehose is never idle)
  and tighten the read-deadline watchdog to 12s for faster reconnect after the
  upstream's periodic eviction (full-firehose browser clients get evicted ~every
  90s; the watchdog recovers it, ~90% duty cycle). Production-bound /ws/position
  is unaffected (plugins connect to us; no eviction).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

go-services/tracker-go/memstate.go

@@ -5,6 +5,7 @@ import (
 	"net/http"
 	"os"
 	"path/filepath"
+	"sort"
 )
 
 // These endpoints are backed by ingest-only in-memory state in the Python
@@ -40,10 +41,15 @@ func (s *Server) handleQuestStatus(w http.ResponseWriter, r *http.Request) {
 
 // GET /vital-sharing/peers (main.py:1800)
 func (s *Server) handleVitalSharingPeers(w http.ResponseWriter, r *http.Request) {
-	writeJSON(w, http.StatusOK, map[string]any{
-		"peers":            []any{},
-		"subscriber_count": 0,
+	if s.ingestor == nil {
+		writeJSON(w, http.StatusOK, map[string]any{"peers": []any{}, "subscriber_count": 0})
+		return
+	}
+	peers, subCount := s.ingestor.vitalSharingPeers()
+	sort.Slice(peers, func(i, j int) bool {
+		return toStr(peers[i]["character_name"]) < toStr(peers[j]["character_name"])
 	})
+	writeJSON(w, http.StatusOK, map[string]any{"peers": peers, "subscriber_count": subCount})
 }
 
 // GET /equipment-cantrip-state/{name} (main.py:4167)