PR 1233: redesign the VNC console, round two

The error sits at the top of the dialog, and the dialog scrolls as soon as the list grows. With two saved shortcuts in a 1280×720 window, deleting the second one with the save refused leaves the dialog scrolled 158px, the error above what you see, and the row still there. It looks like the click did nothing. A screen reader still announces it (role="alert").

On the last row the focus also drops to the page. The rows are keyed by index, and the delete changes the preference before saving and puts it back when the save fails, so the last row's button is removed and created again. The focus is only put back after a save that worked.

Fix: put the focus back after every delete, whatever the save did, and bring the error into view when it shows. Pass B's scratch test fails at 6d71782 and passes with the focus part, with the 73 novnc tests. Where the error sits is Ken's call.

The buttons now stay enabled while a change saves, so the focus stays, and a click that comes in meanwhile returns early without a word. With saves held for 1.5s in the browser, deleting the first row and then the new first row 300ms later sent one save and left two of the three rows. A real save is quicker, so it takes a quick double press or a slow network.

Fix: let the second change wait for the first instead of dropping it: chain it onto the running save, and pick the row by its keys rather than its index, since the index moves.

The settings moved to a new key so that main's saved defaults don't count as choices. That also drops View only, which the current console saves under the old key on main and release-harvester-v1.10 (since v1.10.0-rc1; v1.9 has no such setting). With the old key holding View only on, the console opens with it off, and a click and a key on the screen went out as 3 pointer and 2 key events (dropped by the test). Someone who chose not to touch the VM would be touching it again.

Fix: when the new key isn't there yet, take viewOnly from the old one. Its default is off, so a saved "on" can only be a choice; the display settings still start fresh. Pass B asked it as a question; I'd fix it, since View only is what keeps input away from the VM.

The comment says the console saves only what the user changes, but saveSettings writes the whole set at the first change. Changing JPEG quality alone saves scaling, zoom, View only and compression too (Pass B, on the preview). So a default changed later won't reach anyone who touched any setting: the trap the new key fixes, smaller.

Fix: save only the values that differ from the defaults (loadSettings already falls back one by one), or say in the comment and the test title that the set is saved once one changes.

Holding Ctrl swaps the keys below the toggles, so the F-key that had the keyboard focus is removed and the focus goes to the page. The arrows then do nothing until Tab or a click. Keyboard alone is fine, since the focus is on the toggle, which stays, and so is the mouse alone. It comes from the redesign's key swap, not the new commits; both passes missed it in round one.

Fix: when a toggle changes the keys, put the focus on the toggle.