Add permission checks to user identity accessors that were bypassing
the consent model, allowing plugins to access user data regardless
of whether the user granted user:read permission.
Changes:
- api.cljs: Add user:read checks to getCurrentUser and getActiveUsers
- comments.cljs: Add user:read checks to comment-proxy and
comment-thread-proxy owner/user getters
- file.cljs: Add user:read check to file-version-proxy createdBy getter
When user:read permission is not granted:
- getCurrentUser() returns null
- getActiveUsers() returns empty array
- owner/user/createdBy getters return null
Follows the established pattern from other permission checks in the
plugin API.
Relates to #11137
AI-assisted-by: qwen3.7-plus