fix: restore destructive dialog buttons and document recent updates

Destructive confirmation buttons lost their styling outside the notes page, including the draft-discard Portal. Share button sizing, typography, disabled feedback and theme-aware hover colors across callers, with Electron and contrast regression coverage and design documentation.

Include the update article draft covering v0.13.8 through v0.13.16 and the separately identified 5116613 follow-up, its verification record and article index. The article remains unpublished with screenshots and release details pending.

Validation: 37 focused tests passed, including real Electron capture; typecheck, lint and staged whitespace checks passed. No model calls. The previously documented unrelated HeartbeatCenter full-suite failure was not rerun.

Release note: Destructive confirmation buttons, including the discard-note-draft dialog, now display consistent styling, keyboard focus and disabled feedback in light and dark themes.

UI-DESIGN.md

@@ -68,7 +68,7 @@
 | `--success`、`--success-subtle` | 成功状态 |
 | `--warning` | 警告状态 |
 | `--danger`、`--danger-strong` | 危险文本和状态 |
-| `--danger-solid` | 最终确认按钮等需要反白文字的危险背景 |
+| `--danger-solid`、`--danger-solid-hover` | 最终确认按钮等需要反白文字的危险背景及悬停背景 |
 | `--danger-border`、`--danger-subtle` | 危险入口和失败状态背景 |
 
 浅色与深色具体值只在 `styles.css` 的主题根节点维护。状态组件必须同时显示文字或图标，不能仅靠颜色区分。
@@ -269,6 +269,11 @@
 - `danger-solid`：确认对话框中的最终危险操作。
 - `danger-zone`：设置页中集中展示的高影响操作区域。
 
+`danger-solid` 必须是全局共享类，不依赖页面祖先；通过 Portal 挂到 `body` 后仍须生效。
+尺寸、圆角、字体、间距和禁用状态与 `primary-button`、`secondary-button` 共用规则，
+键盘焦点沿用全局 `button:focus-visible`。背景及可用态悬停使用危险实心色令牌，文字使用
+`--text-on-accent`；禁用时不触发悬停变色。
+
 普通页面不得用实心红色按钮与主操作并列。危险入口必须使用具体动词和对象，例如“删除知识条目”，避免只写“确定”。
 
 ### 6.7 数据表格与活动列表