feat(aliases): support editing model aliases

[faketrader]

Model aliases could be created and deleted, but existing aliases could not be edited. This change makes the alias list the primary page content and moves both creation and editing into a shared dialog.

• Edit the source model, alias name, reasoning effort, and Fast tier.
• Build edits in memory and persist only after validation succeeds, preserving unrelated YAML configuration.
• Reject missing or ambiguous alias mappings instead of modifying an uncertain target.
• Keep the list actions and compact page header on one row across window sizes.

模型别名原先只能创建和删除，无法编辑已有别名。本次调整将别名列表作为页面主体，并让创建与编辑共用弹窗表单。

• 支持修改原模型、别名名称、思考强度和 Fast 请求层级。
• 在内存中完成编辑与校验后再持久化，保留无关 YAML 配置。
• 别名缺失或存在多个同名映射时拒绝修改，避免更新不确定的目标。
• 列表操作按钮和紧凑页头在不同窗口尺寸下均保持单行。

[lzt404]

good job