Embed web assets into the Go binary

Serve /static from embedded assets when no static path override is configured, add static route coverage, and update Docker/docs to reflect embedded-by-default behavior.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

go/webterm/assets_embed.go

@@ -0,0 +1,18 @@
+package webterm
+
+import (
+	"embed"
+	"io/fs"
+	"net/http"
+)
+
+//go:embed static static/* static/js/* static/icons/*
+var embeddedStaticAssets embed.FS
+
+func embeddedStaticFS() (http.FileSystem, bool) {
+	sub, err := fs.Sub(embeddedStaticAssets, "static")
+	if err != nil {
+		return nil, false
+	}
+	return http.FS(sub), true
+}

go/webterm/server.go

@@ -1466,6 +1466,8 @@ func (s *LocalServer) Handler() http.Handler {
 	mux.HandleFunc("/", s.handleRoot)
 	if strings.TrimSpace(s.staticPath) != "" {
 		mux.Handle("/static/", http.StripPrefix("/static/", http.FileServer(http.Dir(s.staticPath))))
+	} else if staticFS, ok := embeddedStaticFS(); ok {
+		mux.Handle("/static/", http.StripPrefix("/static/", http.FileServer(staticFS)))
 	}
 	return s.loggingMiddleware(s.gzipMiddleware(mux))
 }

go/webterm/server_test.go

@@ -221,6 +221,15 @@ func TestRootTerminalPageAndSparklineValidation(t *testing.T) {
 		t.Fatalf("unexpected root page: %q", text)
 	}
 
+	respStatic, err := http.Get(httpServer.URL + "/static/manifest.json")
+	if err != nil {
+		t.Fatalf("static request error = %v", err)
+	}
+	_ = respStatic.Body.Close()
+	if respStatic.StatusCode != http.StatusOK {
+		t.Fatalf("expected 200 for static manifest, got %d", respStatic.StatusCode)
+	}
+
 	resp2, err := http.Get(httpServer.URL + "/cpu-sparkline.svg")
 	if err != nil {
 		t.Fatalf("sparkline request error = %v", err)