docs(skills): gate the usePermissions example on can(), a boolean, and mark its fence

The `usePermissions` hook example in `skills/objectui/guides/auth-permissions.md`
gated two buttons on `check('contacts', 'update', contact)`. `check` answers a
`PermissionCheckResult` object, an object is truthy, and so both buttons rendered
for every user, denied ones included. The fence was unmarked, so
`check-skill-examples` never compiled it.

The example now gates on `can('contacts', 'update')` / `can('contacts', 'delete')`
— the one boolean spelling the guide's neighbouring paragraph already publishes —
annotated `: boolean` so a `check(...)` put back in that position fails to compile.
The record argument is dropped: measured against the built `@object-ui/permissions`
dist with a throwing Proxy as the record, `evaluatePermission` performs zero
property reads on it, and `can()` agrees with `check(..., record).allowed` on every
(role, action) of the guide's own config.

The fence carries the `os:check` marker and is tagged `tsx`, imports `Button`
from `@object-ui/components`, and types `contact` inline, so the gate compiles
it against the built dist from now on (Semantic phase: 16 of 16 ts fences).

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W5y9kRg1YtYaMQYExVLRc2

Author: claude

skills/objectui/guides/auth-permissions.md

@@ -221,14 +221,20 @@ guide does not govern it; the two look alike and are unrelated.
 
 ### usePermissions hook
 
-```typescript
+<!-- os:check -->
+```tsx
 import { usePermissions } from '@object-ui/permissions';
+import { Button } from '@object-ui/components';
 
-function ContactActions({ contact }) {
-  const { check, checkField, getFieldPermissions, getRowFilter } = usePermissions();
+function ContactActions({ contact }: { contact: { salary?: number } }) {
+  const { can, checkField, getFieldPermissions, getRowFilter } = usePermissions();
 
-  const canEdit = check('contacts', 'update', contact);
-  const canDelete = check('contacts', 'delete', contact);
+  // Gate on `can`, which answers a boolean. `check` answers `{ allowed, … }`, and
+  // an object is truthy, so gated on it both buttons render for a denied user
+  // too; its `record` argument reads no field of the record, so none is passed.
+  // `: boolean` is what makes a `check(...)` here fail to compile.
+  const canEdit: boolean = can('contacts', 'update');
+  const canDelete: boolean = can('contacts', 'delete');
   const canSeeSalary = checkField('contacts', 'salary', 'read');
 
   return (