Standbys that answer the client API themselves, behind router.active_active

A standby follows the leader's Ready replicas over the agent port, every
two seconds, and reports back the replicas its router used and the
on-demand models it was asked for. No engine keys travel: every control
plane derives them from the cluster secret. Budgets are raised to the
store's every 30 s. Unheard from the leader for a minute, a standby
passes /v1 on as before. Off by default.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

internal/control/adminapi/routing.go

@@ -0,0 +1,27 @@
+package adminapi
+
+import (
+	"encoding/json"
+	"io"
+	"net/http"
+
+	"gitea.mynodes.xyz/ilker/llmgw/internal/control"
+)
+
+// registerRouting is what a standby answering requests itself reads from the
+// leader, and reports back to it. Reached by the standby through the agent
+// port with its control-plane certificate, like the rest of the forwarded API.
+func (a *API) registerRouting(mux Mux) {
+	mux.HandleFunc("GET /api/v1/routing", func(w http.ResponseWriter, _ *http.Request) {
+		writeJSON(w, http.StatusOK, a.ctl.Routing())
+	})
+	mux.HandleFunc("POST /api/v1/routing/activity", func(w http.ResponseWriter, r *http.Request) {
+		var act control.Activity
+		if err := json.NewDecoder(io.LimitReader(r.Body, 8<<20)).Decode(&act); err != nil {
+			writeError(w, http.StatusBadRequest, err.Error())
+			return
+		}
+		a.ctl.RecordActivity(act)
+		writeJSON(w, http.StatusOK, a.ctl.Routing())
+	})
+}