fix(authz): strengthen permissionMatches warning, complete export coverage

Move the "don't gate on permissionsFor() with permissionMatches" warning
onto permissionMatches itself so it's visible via autocomplete, not just
on AuthzResolver.permissionsFor. Round out exports.test.ts to cover
scopeKey, safeRecord, and AUTHZ_LOCALS_KEY, closing the gap where
dropping either export from index.ts would not fail the test.

packages/authz/src/engine.ts

@@ -54,7 +54,13 @@ export function expandRoles(catalog: AuthzCatalog, roles: readonly string[]): Se
   return out;
 }
 
-/** Exact match, root wildcard, or a namespace wildcard at any depth. */
+/**
+ * Exact match, root wildcard, or a namespace wildcard at any depth.
+ *
+ * Do NOT gate access by matching against `permissionsFor()`'s result — that set
+ * cannot represent a narrow deny beneath a broad grant, so the composition
+ * returns true where `decide()` refuses. Use `decide()` / `can()` instead.
+ */
 export function permissionMatches(granted: Set<string>, permission: string): boolean {
   if (granted.has("*") || granted.has(permission)) return true;
   for (let at = permission.indexOf(":"); at !== -1; at = permission.indexOf(":", at + 1)) {