v0.1.21

Builders Gate 0.1.21

Fixed
- The desktop app had no icon. A 64-bit module handle was being truncated by an
  undeclared ctypes restype, so the icon resource lookup returned NULL and
  Windows used its generic application icon.
- The logo was a hand-redrawing of itself in four places. All are now traced
  from packaging/logo.svg.
- The rail brand painted the whole mark one colour. New --brand-post token
  carries the logo's blue on both grounds.

Added
- "Run anyway" on the uncommitted-changes refusal, with the offending paths
  listed. The route now forwards allow_dirty, which it previously dropped.