Rename Game Maker to Feuerwerk and serve it at /feuerwerk/ (#422)

The editor gets a name of its own that fits beside Brandmauer,
Glutspeicher and Feuerwehr. This is stage 1, 2 and 4 of #422: the
name, the URL and the stored state in the browser. Repository, CI
runners, containers and the GAME_MAKER_* variables follow in stage 3.

- All paths come from SITE_PATH in src/core/site.ts: the API endpoint,
  the data folders, the play page and the base in vite.config.ts. A
  later move is one line instead of fifteen.
- The window title, the sign-in screen, the playground and the README
  say Feuerwerk. The package, __feuerwerkPlay, the take worklet and the
  writing app in Ogg and Matroska follow.
- The session cookie is now feuerwerk_session, so everyone signs in
  once more.
- localStorage keys are now feuerwerk.*. moveOldStoredKeys copies the
  old game-maker.* keys over on the first start, so settings, panel
  sizes and save games survive.
- tools/ci/serve.sh serves the build under /feuerwerk/. The variable
  GAME_MAKER_BASE_URL keeps its name until stage 3.

Outside the repository, nockal.com/feuerwerk/ is a second symlink to
the same tree. nginx sends the bare /game-maker/ folder there with a
301. Everything else under /game-maker/ is still served directly, so
shared play links and the API keep working.

Finding: when nginx redirects a path without a trailing slash or with
a query, the Brandmauer answers with its own 307 to the same URL plus
a slash, placed after the query. A play link would lose its token that
way, which is why only the bare folder is redirected.

Tests:
- Gate on melektaus-atx: CHECK EXIT 0, 307 files, 4756 tests
  (4 new in site.test.ts).
- Counter-check: when the migration misses the old prefix, 3 of the
  4 new tests fail.
- e2e 60 under /feuerwerk/: ALL PASSED, 20 checks.
- From outside: /feuerwerk/ 200, /game-maker/ 301, an old play
  link 200.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tools/lib/auth.mjs

@@ -16,7 +16,7 @@ export const E2E_ADMIN = 'e2e-admin';
 const DATA = resolve(dirname(fileURLToPath(import.meta.url)), '../../data');
 const PASSWORD_FILE = resolve(DATA, 'e2e-password.txt');
 const ADMIN_PASSWORD_FILE = resolve(DATA, 'e2e-admin-password.txt');
-const COOKIE = 'game_maker_session';
+const COOKIE = 'feuerwerk_session';
 
 /** One session per server for the whole process; logging in per request would be pointless load. */
 const cookies = new Map();
@@ -48,7 +48,7 @@ export async function e2eAdminPassword() {
 }
 
 /**
- * Signs in as anyone and answers with a fresh `game_maker_session=…`, uncached – for a step that
+ * Signs in as anyone and answers with a fresh `feuerwerk_session=…`, uncached – for a step that
  * needs a second account beside the tools' own.
  */
 export async function logIn(baseUrl, username, password) {
@@ -68,7 +68,7 @@ export async function logIn(baseUrl, username, password) {
   return set.split(';')[0];
 }
 
-/** `game_maker_session=…` for `Cookie` headers, logging in on first use. */
+/** `feuerwerk_session=…` for `Cookie` headers, logging in on first use. */
 export async function sessionCookie(baseUrl) {
   const cached = cookies.get(baseUrl);
   if (cached) return cached;

tools/lib/projects.mjs

@@ -22,7 +22,7 @@ export const PROJECTS = {
   actor: '3ccb5c67220b',
 };
 
-export const DEFAULT_BASE_URL = 'https://nockal.com/game-maker/';
+export const DEFAULT_BASE_URL = 'https://nockal.com/feuerwerk/';
 
 /**
  * Reads `[projectId] [baseUrl]` from argv, falling back to `defaultId` and to