v0.1.0-alpha.63

Fixes six VT conformance bugs the corpus port exposed. DCS, PM and APC
payloads no longer paint on screen, so a DECRQSS probe from vim or tmux
and a Kitty graphics envelope stop spraying text. HT stops running past
the last column. An OSC interrupted by an ESC no longer leaks its tail.
The CSI and string buffers are bounded.

Adds Nacre: a pale, low-chroma palette on a vertically graded, tinted
chrome ground. Foreground clears AAA and every ANSI pair stays
distinguishable, which the existing light theme does not manage.

The file explorer moves to the leading column and the command history to
the trailing one. Directories get a filled, tinted folder again -- an
outline folder and an outline document are the same shape at 13pt.

Selection now means one thing across the window: a raised surface under
an accent rail, on the tab bar, the sidebar lists and the section strip.

Also fixes a terminal column that could sit below its own floor with both
sidebars open, and prompt-rail anchors that drew as a translucent full
stop.