test(e2e): walk the app shell at every tablet size

tablet-shell.spec.ts runs on WebKit with an iPad profile (webkit-tablet,
in the WebKit job) and on Chromium with an Android tablet profile
(chromium-tablet, in the shards), across iPad mini to iPad Pro 13 in
both orientations, Safari's bars, Split View and Slide Over. It checks
that the shell fills the window and leaves the document nothing to
scroll, that every rail destination scrolls into view on top and takes a
tap, that the scroll cue follows the overflow, that main reaches its
last line clear of the bottom bar, that the page scrolls again after a
sheet and a dialog close, and that a tab strip leaves the vertical pan
to the page.

ui-standards records the shell and rail rules.

docs/contributing/ui-standards.md

@@ -32,10 +32,10 @@ The gaps this section used to list are closed: `TileHeader` carries a `size="sm"
 
 ## 2. Spacing scale
 
-> **Scroll height is shell-owned.** Only `AuthShell` owns the scroll container's height and bottom padding (`pb-20` wrapper + `<md` bottom-nav clearance on `<main>`). Pages/sections never add viewport-height reserves (`min-h-dvh`, `min-h-[calc(100dvh-…)]`), `h-full` chains, or bottom gutters inside the scrolling `<main>`; nested reserves stack on the shell budget and scroll past the last card. One sanctioned exception: the settings-shell grid floor (budget-derived, documented; retune it when shell paddings change). Lists that need their own scrolling use `max-h-* overflow-y-auto overscroll-contain`. Guard: `e2e/settings-overscroll.spec.ts`.
+> **Scroll height is shell-owned.** Only `AuthShell` owns the scroll container's height and bottom padding (`pb-20` wrapper, `pb-24` in the desktop shell, + the phone shell's bottom-nav clearance on `<main>`). The shell itself takes the window's edges (`absolute inset-0`), never `h-dvh`, and `<main>` is the one vertical scroller: the document neither scrolls nor bounces under it. Pages/sections never add viewport-height reserves (`min-h-dvh`, `min-h-[calc(100dvh-…)]`), `h-full` chains, or bottom gutters inside the scrolling `<main>`; nested reserves stack on the shell budget and scroll past the last card. One sanctioned exception: the settings-shell grid floor (budget-derived, documented; retune it when shell paddings change). Lists that need their own scrolling use `max-h-* overflow-y-auto overscroll-contain`. Guard: `e2e/settings-overscroll.spec.ts`.
 
 - **Allowed steps:** `1 / 1.5 / 2 / 2.5 / 3 / 3.5 / 4 / 6 / 8 / 10`. `2.5` and `3.5` are allowed: the medication card's rhythm is built on them, and the in-between steps earn their keep in dense card interiors. `5` (20 px), as in `py-5` or `p-5`, is not allowed; replace it when you touch a file that still has it. `7` (28 px) is not allowed either: it was the old Settings and Admin `pl-7` body gutter, which is gone (§13).
-- **Page frame:** exactly one authenticated container, owned by `AuthShell` (`layout/auth-shell.tsx:318`): `mx-auto max-w-screen-xl px-4 pt-6 pb-20 md:px-6`. Never re-implement it in a page; full-bleed pages opt out via a shell flag, not negative margins. Prose pages (about/privacy/legal): `mx-auto max-w-3xl px-4 py-8 md:px-6 md:py-12`.
+- **Page frame:** exactly one authenticated container, owned by `AuthShell` (`MAIN_CONTENT_WRAPPER_CLASS` in `layout/shell-metrics.ts`): `mx-auto max-w-screen-xl px-4 pt-6 pb-20 md:px-6 shell-desktop:pb-24`. Never re-implement it in a page; full-bleed pages opt out via a shell flag, not negative margins. Prose pages (about/privacy/legal): `mx-auto max-w-3xl px-4 py-8 md:px-6 md:py-12`.
 - **Page rhythm:** root of every page is `space-y-6`. Grouped card sections: `space-y-10` between groups, `space-y-4` inside a group (notifications/integrations pattern). Insights sub-pages join `space-y-6`.
 - **Left reading edge:** page-level text (H1, explainer, section headings) sits at the container edge. Only surfaces that paint a visible border/background may inset their content (`px-4 md:px-6`). A block without a border must not carry horizontal padding.
 - **Grids:** grids **of** cards/tiles = `gap-4`; value read-outs **inside** one card = `gap-x-3 gap-y-2`; form field grids = `gap-4`.
@@ -148,7 +148,7 @@ Forbidden on any Insights card: a hand-rolled icon+title row, a card title centr
 
 ## 9. One scroll floor; sub-shells never re-declare bottom-space
 
-Reinforces §2's "scroll height is shell-owned". Only `AuthShell` owns the scroll container's bottom padding and any viewport-height reserve: the `<main>` clears the mobile bottom-nav (`pb-[calc(4rem+safe-area)]`) and its wrapper clears the Coach FAB (`pb-20`). **No page, section, or sub-shell** adds a `min-h-[calc(100dvh-…)]` / `min-h-dvh` reserve or a `pb-*` bottom gutter inside the scrolling `<main>`; a nested reserve stacks on the shell budget and scrolls past the last card.
+Reinforces §2's "scroll height is shell-owned". Only `AuthShell` owns the scroll container's bottom padding and any viewport-height reserve: the `<main>` clears the mobile bottom-nav (`pb-[calc(4rem+safe-area)]`), or the home indicator in the desktop shell, and its wrapper clears the Coach FAB (`pb-20`, `pb-24` in the desktop shell). **No page, section, or sub-shell** adds a `min-h-[calc(100dvh-…)]` / `min-h-dvh` reserve or a `pb-*` bottom gutter inside the scrolling `<main>`; a nested reserve stacks on the shell budget and scrolls past the last card.
 
 A two-column sub-shell that needs a "don't jump while loading" floor derives it from **one shared source**: `SUB_SHELL_GRID_FLOOR` (`src/components/layout/shell-metrics.ts`); applied to the **grid** (not a column), so the `1fr` content row stretches to fill without over-shooting. It never re-declares the floor per-shell (`AdminShell` drifting to a stale 12rem column reserve is exactly how this recurred). Guard: `e2e/settings-overscroll.spec.ts` covers Settings **and** Admin and measures against each element's content-box bottom, so a redundant sub-shell `pb-*` fails instead of inflating the allowed budget.
 
@@ -156,6 +156,8 @@ A two-column sub-shell that needs a "don't jump while loading" floor derives it
 
 Settings + Notifications are **account utilities, not feature destinations**. They live ONLY in the user/avatar menu (mobile top-bar `DropdownMenu`; desktop sidebar avatar menu, with Settings additionally in the sidebar footer). The mobile "More" overflow hub carries **feature destinations only** (Measurements, Mood, Cycle, Labs, Coach, …), never Settings or Notifications. The hub is `mobileMoreHubDestinations()` = `visibleNavDestinations` minus the primary slots (`/`, `/medications`, `/insights`); it does **not** append the utility tail. `NAV_UTILITY_DESTINATIONS` (`visibleUtilityDestinations()`) feeds the sidebar footer + user menus, not the mobile overflow. Never surface a utility in two menus reachable from the same screen.
 
+The rail's destination list is the one part of the rail that gives up height: the logo band, the footer group and the account row stay pinned, and the list scrolls between them (`overscroll-contain`, no native scrollbar, fades at an edge with more). A mouse gets the height-stepped row density; a finger keeps the 44 px rows, and at an edge with more destinations the rail shows a scroll cue (`sidebar-nav-scroll-cue`) that a tap follows. Guard: `e2e/tablet-shell.spec.ts`.
+
 ## 11. Inline action row; the PageHeader pattern
 
 A title/sentence with an adjacent action is one row, not a wrapping stack: `flex items-start justify-between gap-3`, the text `min-w-0 flex-1` (wraps internally), the action `shrink-0` (stays beside the text, never pushed to its own line). This is the canonical `PageHeader` / `TileHeader` (`right` slot) shape; reuse it (e.g. the dashboard-hero verdict + CTA) instead of a one-off `flex-wrap` row whose `gap-y-*` drops the action below on a full sentence. Keep the mobile tap-target floor (`min-h-11 sm:min-h-9`).