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>

tests/core/auth.test.ts

@@ -23,17 +23,36 @@ afterEach(() => {
 });
 
 describe('HttpAuthStore', () => {
-  it('reads who is signed in, null included', async () => {
-    stubFetch(JSON.stringify({ user: 'e2e' }), { status: 200 });
-    await expect(new HttpAuthStore('/api').session()).resolves.toBe('e2e');
+  it('reads who is signed in and their role, null included', async () => {
+    stubFetch(JSON.stringify({ user: 'e2e', role: 'user' }), { status: 200 });
+    await expect(new HttpAuthStore('/api').session()).resolves.toEqual({ user: 'e2e', role: 'user' });
 
-    stubFetch(JSON.stringify({ user: null }), { status: 200 });
+    stubFetch(JSON.stringify({ user: 'admin', role: 'admin' }), { status: 200 });
+    await expect(new HttpAuthStore('/api').session()).resolves.toEqual({ user: 'admin', role: 'admin' });
+
+    stubFetch(JSON.stringify({ user: null, role: null }), { status: 200 });
     await expect(new HttpAuthStore('/api').session()).resolves.toBeNull();
   });
 
-  it('sends the pair as JSON and answers with the name the server confirms', async () => {
-    const mock = stubFetch(JSON.stringify({ user: 'user' }), { status: 200 });
-    await expect(new HttpAuthStore('/api').logIn('user', 'secret')).resolves.toBe('user');
+  // #180: the weaker reading is the safe one – a server from before roles, or a role this editor does
+  // not know, must not make anyone an administrator.
+  it('takes a missing or unknown role for user', async () => {
+    stubFetch(JSON.stringify({ user: 'old' }), { status: 200 });
+    await expect(new HttpAuthStore('/api').session()).resolves.toEqual({ user: 'old', role: 'user' });
+
+    stubFetch(JSON.stringify({ user: 'odd', role: 'root' }), { status: 200 });
+    await expect(new HttpAuthStore('/api').logIn('odd', 'secret')).resolves.toEqual({
+      user: 'odd',
+      role: 'user',
+    });
+  });
+
+  it('sends the pair as JSON and answers with the name and role the server confirms', async () => {
+    const mock = stubFetch(JSON.stringify({ user: 'user', role: 'user' }), { status: 200 });
+    await expect(new HttpAuthStore('/api').logIn('user', 'secret')).resolves.toEqual({
+      user: 'user',
+      role: 'user',
+    });
     const [url, init] = mock.mock.calls[0]!;
     expect(url as string).toContain('r=auth%2Flogin');
     expect(init?.method).toBe('POST');