Update Ubuntu container references from 25.10 to 26.04

Co-authored-by: richlander <[email protected]>

Author: Copilot

eng/pipelines/installer/helix-queues-setup.yml

@@ -29,7 +29,7 @@ jobs:
 
     # Linux arm64
     - ${{ if eq(parameters.platform, 'linux_arm64') }}:
-      - (Ubuntu.2510.Arm64.Open)Ubuntu.2204.Armarch[email protected]/dotnet-buildtools/prereqs:ubuntu-25.10-helix-arm64v8
+      - (Ubuntu.2604.Arm64.Open)AzureLinux.3.Arm64[email protected]/dotnet-buildtools/prereqs:ubuntu-26.04-helix-arm64v8
 
     # Linux musl x64
     - ${{ if eq(parameters.platform, 'linux_musl_x64') }}:

eng/pipelines/libraries/helix-queues-setup.yml

@@ -31,7 +31,7 @@ jobs:
     # Linux arm64
     - ${{ if eq(parameters.platform, 'linux_arm64') }}:
       - ${{ if or(eq(parameters.jobParameters.isExtraPlatformsBuild, true), eq(parameters.jobParameters.includeAllPlatforms, true)) }}:
-        - (Ubuntu.2510.ArmArch.Open)Ubuntu.2204.ArmArch[email protected]/dotnet-buildtools/prereqs:ubuntu-25.10-helix-arm64v8
+        - (Ubuntu.2604.ArmArch.Open)AzureLinux.3.Arm64[email protected]/dotnet-buildtools/prereqs:ubuntu-26.04-helix-arm64v8
       - ${{ if or(ne(parameters.jobParameters.isExtraPlatformsBuild, true), eq(parameters.jobParameters.includeAllPlatforms, true)) }}:
         - (AzureLinux.3.0.ArmArch.Open)[email protected]/dotnet-buildtools/prereqs:azurelinux-3.0-helix-arm64v8
 
@@ -64,7 +64,7 @@ jobs:
             - (Debian.13.Amd64.Open)[email protected]/dotnet-buildtools/prereqs:debian-13-helix-amd64
             - (Fedora.42.Amd64.Open)[email protected]/dotnet-buildtools/prereqs:fedora-42-helix-amd64
             - (openSUSE.15.6.Amd64.Open)[email protected]/dotnet-buildtools/prereqs:opensuse-15.6-helix-amd64
-            - (Ubuntu.2510.Amd64.Open)[email protected]/dotnet-buildtools/prereqs:ubuntu-25.10-helix-amd64
+            - (Ubuntu.2604.Amd64.Open)[email protected]/dotnet-buildtools/prereqs:ubuntu-26.04-helix-amd64
 
           - ${{ if eq(parameters.jobParameters.testScope, 'outerloop') }}:
               # outerloop only CoreCLR