v0.1.0-alpha.62

Takes the Zig core off the output path. Every byte a child process wrote
was parsed twice and one result discarded; the discarded one cost up to
648 ns/byte on colour-heavy output.

Ports 25 VT cases from the Zig corpus onto the Swift interpreter that
actually renders, which exposed six real conformance bugs -- they are
documented, not yet fixed.

Panes become rounded cards inset on a quiet ground, with the grid inset
sized against the corner radius so no cell is ever clipped and the size
reported to the PTY stays honest.

The sidebar gains an elevated selected row, header rhythm and a reserved
glyph column, which retired an accent rail that was drawn on its own
accent wash and selected-row text that had never been contrast-measured.

Adds a settings-schema linter with 23 structural invariants, after the
same merge conflict broke the build three times. The menu bar wears
Kurotty's own mark instead of a generic terminal glyph.