Update platform version for 261 (#8773)

A problem is that I may need a way for users to download a dev Dart plugin as well.

Another problem is there are many new verify issues for 2026.1 (these can be seen on the jetbrains site already, even though our current plugins aren't technically compatible with 2026.1). Maybe it would make sense to focus on fixing those first, and make this an issue instead so we know that compatibility for 2026.1 is on our agenda.

Author: helin24

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ### Added
 
+- Support for IntelliJ platform version 2026.1. (#8773)
+
 ### Changed
 
 - Improved color recognition in gutter previews by making it more specific to `Colors` and `CupertinoColors` classes. (#8824)

gradle.properties

@@ -4,11 +4,11 @@
 # found in the LICENSE file.
 #
 
-ideaVersion=2025.2.1.5
+ideaVersion=2025.2.3.9
 dartPluginVersion= 502.0.0
 # Also update the versions for verify checks in tool/github.sh.
 sinceBuild=251
-untilBuild=253.*
+untilBuild=261.*
 javaVersion=21
 kotlin.stdlib.default.dependency=false
 org.gradle.parallel=true