ui: share view in the shell, icon rail, phone polish

- shared view uses the bar, porthole and status band; outline gets its own
  window on wide screens; j/k, gg/G, Ctrl-d/u scroll with a vim-style ruler
- rail doors are line icons in groups with hover tooltips and keycaps
- phone: number-only space pills, no nested rims, icon dock, toast messages,
  back button and one-line meta in the document header
- keycaps (.kbd) wherever keys are shown, styled scrollbars in Chrome,
  outline tracks position on jumps, breakpoints unified at 767px

web/src/lib/commands.ts

@@ -1,9 +1,8 @@
 import { api, type BackupStatus } from './api'
 import { workspace } from './store.svelte'
-import { formatDay, parseDay } from './util'
+import { formatDay, parseDay, type ScrollAmount } from './util'
 
-/** How far the reading pane is asked to scroll: lines, a half page, or an end. */
-export type ScrollAmount = number | 'top' | 'bottom' | 'halfdown' | 'halfup'
+export type { ScrollAmount }
 
 /** Filled in by App.svelte so ex-commands can reach the DOM-bound bits. */
 export const hooks = {