0.22.0-alpha

Added

• --diff-layers: --diff's per-layer sibling. Raised by the repo owner while reading a real
  multi-hop --diff: there was no way to tell which layer (Environment, Client, or one specific
  Host) produced a given changed line without separately running --list and reasoning it out by
  hand. --diff-layers prints one diff per layer that actually changes the resource instead of one
  diff comparing the base file straight to the final merged result — computed by re-running the
  same merge with one more patch applied each time, needing zero changes to any of the four format
  engines since LayerMerge already accepts an arbitrary prefix of the ordered patch list. Each
  section is tagged [<layer>], or [<layer> overrides <earlier layer>] when every line it
  changes was last touched by that one earlier layer; a hunk that re-touches lines with different
  prior owners gets a plain [<layer>] tag instead, with a (overrides <layer>) note on each
  individual changed line that has one (LayerDiffAttribution, reusing GitDiff.Render's own
  unified-diff hunk headers for line-position bookkeeping rather than a second diff engine).
  Mutually exclusive with --diff. See docs/DIFF_LAYERS_DESIGN.md for the full design and status.