nomos+web: streaming, provider routing, event gap-fill, embedded UI; fix approval FK & session context

Agent (cmd/nomos):
- Stream LLM tokens via NewStreaming; emit text_delta then final text.
- OpenRouter provider routing: data_collection=deny (ZDR) + require_parameters;
  NOMOS_PROVIDER_SORT opt-in; Exacto via model suffix.
- Multi-turn: reload session history into context; UI passes session id.
- Fix agent_activity logging (agent_id/session_id) and mcpClient data race.

Events (live control-room feed):
- approval.created (mcp), approval.decided (api), execution.completed/failed
  (approved-action path), signal.raised/resolved + health.changed (scheduler,
  transition-gated).

Fixes:
- createApproval FK violation (reuse execution entity) — the agent's only
  write path; log the previously-swallowed errors.

Web UI:
- Embed web/dist via //go:embed (single binary); Dockerfile builds SPA into
  the Go stage; committed .gitkeep placeholder keeps backend-only builds green.
- Caddy: Authentik-gated /agent/* -> nomos so the UI reaches the agent
  same-origin in production.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

internal/httpapi/server.go

@@ -15,6 +15,9 @@ import (
 	"log/slog"
 	"math/big"
 	"net/http"
+	"net/http/httputil"
+	"net/url"
+	"os"
 	"strings"
 	"sync"
 	"time"
@@ -66,7 +69,7 @@ type secretsBackend interface {
 // holds a dedicated pooled connection for LISTEN. Callers MUST cancel ctx
 // before closing the pool — otherwise the held connection never releases
 // and pool.Close() deadlocks.
-func NewHandler(ctx context.Context, pool *db.Pool, cfg config.Config) http.Handler {
+func NewHandler(ctx context.Context, pool *db.Pool, cfg config.Config, uiHandler http.Handler) http.Handler {
 	s := &Server{
 		pool:      pool,
 		cfg:       cfg,
@@ -148,6 +151,24 @@ func NewHandler(ctx context.Context, pool *db.Pool, cfg config.Config) http.Hand
 	}
 	r.With(combinedAuth(cfg)).Handle("/mcp", mcphandler.NewHandler(pool, cfg.MCPBearerToken, nomosAgentID))
 
+	r.Get("/ui/*", func(w http.ResponseWriter, req *http.Request) {
+		if uiHandler != nil {
+			uiHandler.ServeHTTP(w, req)
+		}
+	})
+	r.Get("/ui", func(w http.ResponseWriter, req *http.Request) {
+		http.Redirect(w, req, "/ui/", http.StatusMovedPermanently)
+	})
+	r.Get("/", func(w http.ResponseWriter, req *http.Request) {
+		http.Redirect(w, req, "/ui/", http.StatusMovedPermanently)
+	})
+
+	if nomosURL := os.Getenv("NOMOS_PROXY_URL"); nomosURL != "" {
+		target, _ := url.Parse(nomosURL)
+		proxy := httputil.NewSingleHostReverseProxy(target)
+		r.Mount("/agent", http.StripPrefix("/agent", proxy))
+	}
+
 	return r
 }
 
@@ -484,10 +505,10 @@ func requestLogger(next http.Handler) http.Handler {
 
 // ListenAndServe runs the API server with graceful shutdown on ctx cancel
 // (SG4): stop accepting, drain in-flight for up to 30s, then exit.
-func ListenAndServe(ctx context.Context, pool *db.Pool, cfg config.Config) error {
+func ListenAndServe(ctx context.Context, pool *db.Pool, cfg config.Config, uiHandler http.Handler) error {
 	srv := &http.Server{
 		Addr:              cfg.APIListen,
-		Handler:           NewHandler(ctx, pool, cfg),
+		Handler:           NewHandler(ctx, pool, cfg, uiHandler),
 		ReadHeaderTimeout: 10 * time.Second,
 	}