Swipes take a longer drag and slide the reader across (#49)

At a flat 60px, a thumb scrolling slightly on the diagonal moved on to the next item by
accident. A swipe now has to cover a quarter of the reader's width, and never less than 100px,
and the reader follows the finger while it is down, so it is plain before letting go whether it
will move on. It slides off on a swipe and the next item slides in from the other side; a short
one springs back. The CHANGELOG also gets back the [0.8.3] link a stray edit had broken.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -7,6 +7,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Swiping to the next or previous item takes a longer swipe, a quarter of the screen, so a
+  diagonal scroll no longer jumps ahead by accident. The item follows your finger and slides
+  across as it changes.
+
 ## [0.8.4] - 2026-09-19
 
 ### Added