fix(settings): 弹窗高度补 vh 基线，分区菜单去掉强调条（BUG-698）

设置弹窗的固定高度只用 dvh 写、没有回退。不认识该单位的引擎会把整条
height 与 max-height 作废，盒子退回按内容撑开，于是切分区就跳大小——
这正是 BUG-554 现象的复发，而 BUG-554 的防复发「必须同时声明 width 与
height」只检查声明存不存在，挡不住「写了但没生效」。

实测（Chrome 151，真实产物 CSS + 复刻 DOM，1440×900）：dvh 正常时四个
分区恒定 866.80×640px，**事故不复现**；摘掉 dvh 后变成 313/313/378/1130，
宽度不动——与用户描述的形状完全一致。因此机制已证实，但用户当时的浏览器
未定位，BUG-698 记为 investigating 而非 resolved。

附带发现：任务书要求照抄的重复声明式回退 `height: 100vh; height: 100dvh;`
在本仓根本发布不出去——Lightning CSS 会合并同名属性的重复声明只留最后一条，
全仓唯一那处回退（sidebar-provider）在线上早就是死的，还有一条测试专门守着
这个从未发布过的写法。改用 @supports (height: 1dvh)：vh 作基线，dvh 作升级。
修复后不支持 dvh 的引擎也收敛到恒定 640px，支持的逐像素无变化。

同轮按产品决策去掉设置分区菜单的左侧/下方强调色条，选中与悬停改用面与
墨色等级区分，不用色相、不用字重。左侧会话列表的色条本轮不动。

- 新增 viewport-unit-fallback-contract（3 条，全文件），三次破坏性验证各自打红
- account-dialog-overlay 新增同尺寸契约与分区菜单契约
- 三条钉死旧 dvh 字面量的既有断言按「原值/新值/原因」更新，均未弱化
- tsc 0 错；lint 0 error / 118 warning（持平）；npm test 3346/3300/fail 31，
  失败清单与基线逐字相同；/ 仍 ○ Static；样式 gzip +0.38%；
  快速门 pytest 段 792 passed / 1 skipped / 0 failed

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JUei7K13cYxLHE3Axe4A45

frontend/DESIGN.md

@@ -57,7 +57,9 @@ a fourth needs a reason:
    a transparent row (`--color-action`, deepening to `--color-action-hover`).
    Never a filled block: a full-width terracotta surface would break the
    ninety-percent-light rule.
-2. The 2px bar on the active session (`--sidebar-ring`).
+2. The 2px bar on the active session (`--sidebar-ring`). This is the sidebar only —
+   the settings dialog's pane menu carries no accent bar and separates hover from
+   current with surface and ink rank instead.
 3. The profile initial's circle (`--color-action`), which only renders when the
    account has no uploaded avatar.
 
@@ -170,7 +172,7 @@ Radii have two visual steps. Controls use 8px (`--radius-md`; `--radius-xs` and
 - Desktop shell: 288px sidebar plus flexible reading panel.
 - Layout breakpoints: mobile below 768px, tablet 768–1023px, desktop 1024px and above. These three decide the shell — sidebar mode, grid columns, drawer versus rail. CSS `@media` width cuts must follow `sidebarViewportForWidth` in `frontend/src/lib/sidebar-state.ts` (768 / 1024), not the other way around. The allowlist lives as a comment at the top of `globals.css` and is locked by `frontend/tests/viewport-breakpoint-contract.test.ts`.
 - Allowed `@media` widths: 480 (small phone), 640/641 (content grids: membership, rectification candidates, intake card), 767/768 (mobile/tablet), 860 (report TOC, content width of the third column), 1023/1024 (tablet/desktop). Do not add a new width without updating that list and the contract test in the same change.
-- All full-height surfaces use `100dvh`. Touch targets: on a coarse pointer the hit is 44×44; the visual control may stay smaller. Message-action icons stay 26×26; a fine pointer keeps the 27×34 overlay, a coarse pointer opens gap and bottom margin to 20px so a 44×44 overlay does not eat the next button or the follow-up pills. Locked by `frontend/tests/touch-target-contract.test.ts`.
+- All full-height surfaces use `100dvh`, but never as the only declaration. A `dvh` length is dropped whole by an engine that does not know the unit, and a `height` that vanishes falls back to the content height — which is how the settings dialog started resizing per pane (BUG-698). Write the plain `vh` value as the base and upgrade inside `@supports (height: 1dvh)`. Do **not** use the duplicate-declaration form `height: 100vh; height: 100dvh;`: Lightning CSS (Tailwind v4's minifier) collapses duplicate declarations of one property and keeps only the last, so the fallback never reaches the browser. Locked by `frontend/tests/viewport-unit-fallback-contract.test.ts`. Touch targets: on a coarse pointer the hit is 44×44; the visual control may stay smaller. Message-action icons stay 26×26; a fine pointer keeps the 27×34 overlay, a coarse pointer opens gap and bottom margin to 20px so a 44×44 overlay does not eat the next button or the follow-up pills. Locked by `frontend/tests/touch-target-contract.test.ts`.
 
 ## 5. Components
 
@@ -392,7 +394,8 @@ Text release is paced, not animated: the frame buffer commits at most once per a
 ### Settings dialog
 
 - **Structure:** one fixed chrome for four panes — 个人资料, 星盘资料, 账户与点数, 通用设置. Left nav is 176px and does not scroll; the title bar stays put; only the right-hand content pane scrolls. Logout stays a separate 400px confirmation.
-- **Width / height:** desktop `width: min(100vw - 32px, 880px); height: min(84dvh, 640px)`. Switching panes does not change the frame. At ≤767px the dialog is full-screen with four equal tabs along the top.
+- **Width / height:** desktop `width: min(100vw - 32px, 880px)`, with `height: min(84vh, 640px)` as the base and `min(84dvh, 640px)` applied inside `@supports (height: 1dvh)`. All four panes share one class (`.settings-modal`), so switching panes cannot change the frame. At ≤767px the dialog is full-screen with four equal tabs along the top.
+- **Pane menu states:** default is transparent with secondary ink; hover is a 55% wash of `--color-canvas-muted` keeping secondary ink; current is the solid muted surface with primary ink. No accent bar, and no weight change — hierarchy here comes from ink rank and surface, matching “Hierarchy inside the nav comes from ink rank, not hue”. The sidebar's 2px `--sidebar-ring` on the active session is deliberately **not** changed to match; the two surfaces read differently on purpose until that is revisited.
 - **Personal profile:** one row of avatar editing (48px preview, eight palettes, 换一个形象) plus nickname and login email. No duplicate 管理星盘资料 button.
 - **Chart library:** list first (self row, other rows, 添加其他人). A row opens a detail with ← 星盘资料. Other details own 设为默认 / 删除 / 用于合盘 and that person's synastry history. The add form is a view, not an always-on stack.
 - **States:** open, pane switch, list / self / other / add, saving, success, and error.