feat(web): split SPA from oikos binary, require auth on every route

Phase 0 of plans/2026-07-12-wails-desktop-app.md. The control-room SPA
is no longer embedded (web/embed.go deleted); it's a standalone static
build served separately (make ui / make deploy-ui). The api process
adds CORS and drops the dev-open auth bypass — every route now needs a
real bearer token, including SSE (?token= query param, EventSource
can't set headers) and api's own /agent proxy to nomos (previously
unauthenticated by omission).

nomos was an unauthenticated client of api's /mcp and approval-decision
endpoints; closing dev-open would have broken it, so it now sends
Authorization: Bearer $OIKOS_MCP_BEARER_TOKEN on every call back to api.

SPA gets a runtime config module (config.ts) and a Config.svelte
first-launch/reconfigure page, reachable afterwards via a "Connection"
entry in the sidebar footer. Every fetch() in api.ts routes through
fetchWithAuth so the same build works same-origin (browser prod, Vite
dev proxy) or cross-origin (future Wails webview, remote access).

Six gaps found against the plan and the live Caddy topology while
implementing — documented in the plan's "Plan review" section, most
notably: api's own /agent mount was never behind combinedAuth (fixed),
and production's Authentik forward-auth needs a bearer-token bypass for
API routes that this repo's Caddyfile.oikos reference copy now has, but
the real dtoro/caddy-conf deploy does not yet.

Verified live: cross-origin static SPA + API, CORS, bearer auth, SSE
query-token auth, and localStorage persistence all confirmed working
in-browser. Full Go test suite and npm run build pass with no
regressions against the pre-change baseline.

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

cmd/oikos/main.go

@@ -1,17 +1,14 @@
 package main
 
 import (
-	"bytes"
 	"context"
 	"fmt"
-	"io"
 	"log/slog"
 	"net/http"
 	"os"
 	"os/signal"
 	"strings"
 	"syscall"
-	"time"
 
 	"github.com/dtoro/oikos/internal/config"
 	"github.com/dtoro/oikos/internal/db"
@@ -21,50 +18,9 @@ import (
 	"github.com/dtoro/oikos/internal/observability"
 	"github.com/dtoro/oikos/internal/scheduler"
 	"github.com/dtoro/oikos/internal/secrets"
-	"github.com/dtoro/oikos/web"
 	"github.com/jackc/pgx/v5"
 )
 
-// uiHandler serves the control-room SPA from assets embedded at build time
-// (web/embed.go), with SPA fallback to index.html. Requests arrive as /ui/*;
-// the /ui prefix is stripped to index into the embedded dist/ tree. Files are
-// written via http.ServeContent (not http.FileServer) to avoid its
-// index.html -> "./" canonical redirect, which loops for /ui/.
-func uiHandler() http.Handler {
-	dist, err := web.DistFS()
-	if err != nil {
-		slog.Warn("ui: embedded assets unavailable", "error", err)
-		return http.NotFoundHandler()
-	}
-	serve := func(w http.ResponseWriter, r *http.Request, name string) bool {
-		f, err := dist.Open(name)
-		if err != nil {
-			return false
-		}
-		defer f.Close()
-		data, err := io.ReadAll(f)
-		if err != nil {
-			return false
-		}
-		http.ServeContent(w, r, name, time.Time{}, bytes.NewReader(data))
-		return true
-	}
-	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		name := strings.TrimPrefix(strings.TrimPrefix(r.URL.Path, "/ui"), "/")
-		if name == "" {
-			name = "index.html"
-		}
-		if serve(w, r, name) {
-			return
-		}
-		// SPA fallback: serve index.html for unknown client-side routes.
-		if serve(w, r, "index.html") {
-			return
-		}
-		http.NotFound(w, r)
-	})
-}
-
 var schedulerRunner = scheduler.RunnerForMain()
 var notifierRunner = notifier.RunnerForMain()
 
@@ -129,7 +85,7 @@ func main() {
 		go notifierRunner(ctx, pool, cfg)
 
 		slog.Info("all: starting api with scheduler + notifier in background")
-		if err := httpapi.ListenAndServe(ctx, pool, cfg, uiHandler()); err != nil {
+		if err := httpapi.ListenAndServe(ctx, pool, cfg); err != nil {
 			slog.Error("api failed", "error", err)
 			os.Exit(1)
 		}
@@ -308,7 +264,7 @@ func runAPI(ctx context.Context, cfg config.Config) error {
 		return fmt.Errorf("migrations: %w", err)
 	}
 
-	err = httpapi.ListenAndServe(ctx, pool, cfg, uiHandler())
+	err = httpapi.ListenAndServe(ctx, pool, cfg)
 	if err == http.ErrServerClosed {
 		return nil
 	}