feat: evaluate content permissions tools

[pandaria75]

背景

后续如果 BookStack 用于团队协作，可能需要读取或设置内容权限。

但权限操作风险较高，不适合早期直接暴露给 Agent。

目标

评估 BookStack content permissions API 是否适合作为插件工具。

非目标

当前不实现权限修改。

验收标准

• 梳理读取权限和更新权限的能力。
• 说明安全风险。
• 给出是否仅实现 read-only permissions 工具的建议。

[pandaria75]

Completed evaluation for #48 in task planning artifacts.

Summary:

• BookStack content-permissions APIs are security-sensitive because they reveal or alter access-control state.
• A future read-only inspection tool may be useful for trusted admin/debug workflows.
• Permission-changing behavior is not appropriate for this task and should not be exposed casually to LLM automation.

Recommendation:

• Priority P2 for later read-only evaluation only.
• Keep any future write/change capability behind separate approval and stronger governance.

No production implementation for #48 is included in this task.