[httpsphl]

Two things the owner asked after using 0.9.1 + main:

Switching between browser, terminal and files was not fluid

• The three panels share one width (botloft.panel.computer, 600 px to start), so switching never changes the width. Before, files was 416 px: going there popped, coming back slid part of the way.
• The dock moved to a fixed footer at the same place in the three panels, so it stays still.
• A panel replacing another (dock or header buttons) no longer slides in: its content fades up 4 px in 220 ms (panel-swapped); the dock and the resize handle stay still.
• Coming back shows the last browser frame and the last commands at once while they load again (cached per connection).

The page in the browser was tiny

• The page was always 1280 px wide, so a ~650 px panel showed it at half size. Now the page takes the room's width, from 800 to 1600 px, with the height in the room's shape (600-2000), so it shows near its real size. Below 800 px the image shrinks instead, to keep the desktop layout. With nobody watching it is still 1280×800.
• The desk around the page is thinner (10/26 px), and the dock no longer takes room inside it.
• Spec 15.1, 21.3 and 21.8 updated.

Test plan

• cargo fmt, clippy -D warnings, cargo test --workspace (viewport unit tests, browser_panel.rs with the real Edge for the new sizes)
• pnpm check (room size, swap class on dock switch)
• Preview: same width across the dock, footer dock, larger page
• Real app: open a site like Gmail in a bot's browser and check it is readable; switch with the dock