fix(auth): stop hasPermission crashing for non-admin ("user") roles

hasPermission()'s parameter was named userRole: string, shadowing the
module-level userRole role object exported earlier in the same file.
The internal roles map's `user: userRole` entry therefore bound to the
shadowed string parameter (e.g. "user") instead of the actual role
object — so any permission check for a "user"-role session (the only
non-admin role in the app) hit `"user".statements[resource]`, which is
undefined, and threw instead of returning false.

Net effect: every requirePermission()-gated route in the app returned
a 500 instead of a 403 for non-admin users. This predates phase 14 —
surfaced now because phase 14's PAX8 resolve route is admin-gated and
got exercised by a non-admin account during verification.

Renamed the parameter to roleName to remove the collision. Added
lib/permissions.test.ts (previously zero coverage on this file) to
lock in the "user"/admin/super-admin behavior and prevent regression.

lib/permissions.test.ts

@@ -0,0 +1,25 @@
+import { describe, it, expect } from 'vitest';
+import { hasPermission } from './permissions';
+
+describe('hasPermission', () => {
+  it('returns false (not a crash) for a "user" role on an admin-only resource', () => {
+    expect(() => hasPermission('user', 'admin', 'access')).not.toThrow();
+    expect(hasPermission('user', 'admin', 'access')).toBe(false);
+  });
+
+  it('returns true for "admin" role on an admin-gated resource', () => {
+    expect(hasPermission('admin', 'admin', 'access')).toBe(true);
+  });
+
+  it('returns true for "super-admin" role on an admin-gated resource', () => {
+    expect(hasPermission('super-admin', 'admin', 'access')).toBe(true);
+  });
+
+  it('returns true for "user" role on a permitted resource', () => {
+    expect(hasPermission('user', 'tickets', 'read')).toBe(true);
+  });
+
+  it('returns false for an unknown role', () => {
+    expect(hasPermission('bogus-role', 'admin', 'access')).toBe(false);
+  });
+});