fix(edit): curate the CalDAV colour picker (#22)

CalDAV sync adapters (DAVx5) publish all ~147 CSS3 named colours into
CalendarContract.Colors, so the event-colour picker showed a full screen
of alphabetically-scrambled, partly duplicated swatches.

Curation now runs in the space the picker actually paints — every swatch
is softened through pastelize, which pins lightness and caps saturation,
so the raw palette's lightness axis is invisible on screen. Judging
distinctness there: colours that paint identically collapse to one
(folding aliases, dark/light shades of a hue, and the neutrals together),
oversized palettes drop washed-out neutral-origin tints and thin by CIE76
ΔE in painted Lab, and survivors sort continuously by painted hue with the
wheel cut at its single widest gap. The CSS3 dump lands at ~33 distinct,
rainbow-ordered swatches; small hand-picked palettes (Google's) pass
through untouched. Every surviving swatch keeps its provider colour key so
picks still round-trip through sync.

This revives work stranded on fix/caldav-color-picker (never merged) and
adapts it to the floret-kit extraction of pastelize: the curation's
painted-space transform now lives self-contained in domain/pastelArgb as a
mirror of floret's pastelize shaping, rather than the two sharing one
function.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -5,6 +5,19 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Fixed
+- A tidy colour picker on CalDAV calendars. For calendars synced by a CalDAV
+  app (such as DAVx5), the event colour picker showed every colour the account
+  publishes — nearly 150 swatches in alphabetical order, many of them
+  duplicates or near-identical shades. The picker now shows only visually
+  distinct colours, arranged as a rainbow; near-duplicate shades and the
+  washed-out neutrals are folded away so no two swatches look alike. Picked
+  colours still sync exactly as before, and calendars with hand-picked
+  palettes (like Google's) are unaffected. Thanks to @ptab for the report
+  ([#22]).
+
 ## [2.14.0] — 2026-07-06
 
 ### Added
@@ -865,6 +878,7 @@ automatically, with zero telemetry and no internet permission.
 [#18]: https://codeberg.org/jlmakiola/calendula/issues/18
 [#19]: https://codeberg.org/jlmakiola/calendula/issues/19
 [#20]: https://codeberg.org/jlmakiola/calendula/issues/20
+[#22]: https://codeberg.org/jlmakiola/calendula/issues/22
 [#24]: https://codeberg.org/jlmakiola/calendula/issues/24
 [#25]: https://codeberg.org/jlmakiola/calendula/issues/25
 [#27]: https://codeberg.org/jlmakiola/calendula/issues/27