A stateful, image-owning converter for the desktop tuning loop. The consumer
calls render / render_svg / render_with_progress with a fresh Config each
frame and never reasons about cachability: Session compares the Config's
SegmentKey (its clustering-relevant projection — color mode, color precision,
layer difference, speckle, binary threshold settings) to what it last
clustered and re-segments only when that changes. Everything else — fit mode,
curve params, compositing, palette, optimization — reuses the cached
Segmentation.
Config::segment_key is public too, so callers that hold their own state (e.g.
the wasm/JS side) can compare keys with the same source of truth.
Tests cover the key partition (finish-phase params share a key; clustering
params change it) and that Session output matches the one-shot pipeline for
both a reused-segmentation render and a re-segmented one.
Add desktop app screenshot referenced by the README
Condense the unreleased changelog notes
Chris Tsang
