Add FxNode render graph playground

Add persistent render graph loadouts, grouped node authoring, code-appending apply behavior, explicit playground lighting, and resilient worker startup.

Amp-Thread-ID: https://ampcode.com/threads/T-01a033d4-0e44-708e-af0e-6166283416ff
Co-authored-by: Heaust Azure <heaust.azure@gmail.com>

server/app_test.go

@@ -2,6 +2,8 @@ package main
 
 import (
 	"bytes"
+	"context"
+	"database/sql"
 	"encoding/json"
 	"net/http"
 	"net/http/httptest"
@@ -66,12 +68,52 @@ func TestHealth(t *testing.T) {
 	}
 }
 
+func TestPlaygroundStoreMigratesLoadouts(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "legacy.db")
+	database, err := sql.Open("sqlite3", path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := database.Exec(`
+		CREATE TABLE playgrounds (
+			id TEXT NOT NULL,
+			revision INTEGER NOT NULL,
+			title TEXT NOT NULL,
+			code TEXT NOT NULL,
+			created_at TEXT NOT NULL,
+			PRIMARY KEY (id, revision)
+		)
+	`); err != nil {
+		database.Close()
+		t.Fatal(err)
+	}
+	if err := database.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	store, err := openPlaygroundStore(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { store.Close() })
+	saved, err := store.save(context.Background(), "", "Migrated", "const migrated = true;", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(saved.Loadouts) != "[]" {
+		t.Fatalf("loadouts = %s", saved.Loadouts)
+	}
+}
+
 func TestSaveAndLoadPlaygroundRevision(t *testing.T) {
 	app := testApplication(t)
 	handler := app.routes()
-	requestBody, _ := json.Marshal(map[string]string{
+	requestBody, _ := json.Marshal(map[string]any{
 		"title": "First scene",
 		"code":  "const scene = true;",
+		"loadouts": []map[string]any{{
+			"id": "custom", "name": "Custom", "layout": map[string]any{},
+		}},
 	})
 	request := httptest.NewRequest(http.MethodPost, "/api/playgrounds", bytes.NewReader(requestBody))
 	response := httptest.NewRecorder()
@@ -118,6 +160,17 @@ func TestSaveAndLoadPlaygroundRevision(t *testing.T) {
 	if loaded.Code != "const scene = true;" || loaded.Title != "First scene" {
 		t.Fatalf("loaded = %#v", loaded)
 	}
+	var loadouts []struct {
+		ID     string         `json:"id"`
+		Name   string         `json:"name"`
+		Layout map[string]any `json:"layout"`
+	}
+	if err := json.Unmarshal(loaded.Loadouts, &loadouts); err != nil {
+		t.Fatal(err)
+	}
+	if len(loadouts) != 1 || loadouts[0].ID != "custom" || loadouts[0].Name != "Custom" || len(loadouts[0].Layout) != 0 {
+		t.Fatalf("loadouts = %s", loaded.Loadouts)
+	}
 
 	request = httptest.NewRequest(http.MethodGet, "/api/playgrounds/"+saved.ID+"/2", nil)
 	response = httptest.NewRecorder()