Add roles and a user management tab for admins (#180, #179)

Until now every account could do the same, and managing accounts
meant running make-user.php on the server. Accounts now carry a role,
and admins get a tab in the editor to create, rename, re-role, reset
and delete accounts. Both issues share the same server files, so they
land in one commit.

#180 Roles:
- Every account is admin or user. A missing or unknown role counts as
  user, on the server and in the client.
- auth/session and auth/login return {user, role}.
- Auth::requireAdmin() answers everyone else with 403.
- make-user.php takes the role as a third argument. Without it an
  existing account keeps its role, so a password reset from the CLI
  never demotes an admin.
- Admins see and save other users' projects like their own. Saving
  keeps the original owner.

#179 User management:
- The account menu gets "User management" (admins only) and "Plugins"
  (everyone). Both open the same closable tab, accounts on top and
  plugins below. The fixed Plugins tab is gone.
- Per account: Rename, Role, Password (no old password needed) and
  Delete with a confirmation. "New user..." creates one.
- Each account lists its projects with an Open button.
- Delete is refused while the account still owns projects.
- Renaming moves the projects along and ends every session of the
  account. transfer takes the same lock as save.
- On their own row an admin can only set the password. The last admin
  cannot be demoted or deleted. The server enforces both.
- The account rules live in AccountRules.php and accountRules.ts as
  pure functions, so they are testable without a server.

Findings:
- At 1280 px the Delete button reached past the column edge and was
  not clickable. The name column is flexible now, and module 49 checks
  the layout.
- The server lets an admin delete other users' projects, but the
  editor has no button for it yet. Left open in the issue.

Tests:
- ./check.sh: 148 files, 2214 tests, exit 0 (was 147 / 2204).
- New tests/php/accounts.test.php, 51 checks, plain PHP. CI runs it
  as its own step in the gate job, the host has no PHP.
- New e2e module 49 with 18 checks. CI creates the e2e-admin account
  in serve.sh. Modules 14, 38, 46 and the scaffold follow the new tab.
- e2e 1-16,37,38,45,46,49: all passed, 581 checks.
- Counter-checks: owner on save, admin view, default role and self
  delete in PHP fail 7, 5, 5 and 1 checks. Unchecked requireAdmin,
  a wider column and the caller as owner each fail exactly their
  e2e check.
- Check sum 1314 -> 1333 (+1 in 38, +18 in 49), computed.

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

src/editor/debug/uiHooks.ts

@@ -5,6 +5,7 @@ import { currentFontPicker } from '../font/FontPicker';
 import { currentSoundPicker } from '../sound/SoundPicker';
 import { rectOf, textProbe } from '../textProbe';
 import { currentImagePicker } from '../texture/ImagePicker';
+import type { UsersPane } from '../users/UsersPane';
 import { Color, type ColorSource, type Container, Text } from 'pixi.js';
 import { centreOf, type HookContext } from './hookHelpers';
 
@@ -168,6 +169,26 @@ export function uiHooks({ app, state, editor }: HookContext) {
     tabRow: () => editor.tabRow(),
     /** The open "Change password" dialog (#182): its message and whether it is waiting, or null. */
     passwordDialog: () => editor.accountDialog()?.info() ?? null,
+    /**
+     * The user management (#179); `pane()` is null for an account that is no administrator.
+     * `buttonAt` takes an action (`rename`, `role`, `password`, `delete`) or `open:<project id>`.
+     */
+    users: {
+      pane: () =>
+        editor.usersPane ? { visible: editor.tab === 'management', ...editor.usersPane.debugInfo() } : null,
+      buttonAt: (username: string, action: Parameters<UsersPane['buttonOf']>[1]) => {
+        const button = editor.usersPane?.buttonOf(username, action);
+        return button
+          ? { ...centreOf(button), right: rectOf(button).x + button.w, enabled: button.enabled }
+          : null;
+      },
+      /** The list on screen, for checks that its rows fit into it. */
+      rect: () => (editor.usersPane ? rectOf(editor.usersPane) : null),
+      /** The open form: its title, the message under it, whether it waits, its role (null without a picker). */
+      dialog: () => editor.usersPane?.currentDialog()?.info() ?? null,
+      /** Reads the list again and answers once it is drawn – `json()` does not wait for a promise, `evaluate()` does. */
+      reload: () => editor.usersPane?.reload(),
+    },
     /** The project's collision layers (#152), and the names the open dialog holds (null when shut). */
     collisionLayers: () => ({
       project: [...state.project.collisionLayers],