Promote Unreleased to v1.4.0

Minor bump (per AGENTS.md §12): the section adds SVG diff rendering
(text + rasterized image) — a user-facing feature — alongside a row
tinting behaviour change and six bug fixes covering binary detection
(UTF-16/32), inline-mode highlighting, intra-line-off yellow misuse,
adjacent-rect gap stripes, asymmetric-pair suppression in Both view,
and inline-mode source-file line numbers.

AI-Local-Session: 4519f6b6-393a-4476-8efa-410e5396c3a9
AI-Cloud-Session: 72f9e474-60ab-42c2-b2a0-28fee827cbbb
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Geeven Singh

CHANGELOG.md

@@ -12,6 +12,8 @@ body. Keep section headings exact and write notes in Markdown.
 
 ## [Unreleased]
 
+## [1.4.0] - 2026-05-29
+
 ### Changed
 
 - **Lines with no intra-line spans now paint with the strong