Added support for italic, underline, and strikethrough styling for TextInput: Implements italic underline and strikethrough styling for TextInput (#15563)
Added @react-native-windows/perf-testing, a component performance testing framework for RNW Fabric: [Fabric]: Performance Tests for React Native Windows (#15666)
Expose AutomationOption Setter for ChildSite, allowing other content islands connected in childsite to customize their automation option: Expose AutomationOption Setter for ChildSite (#15622)
Adds support for detecting which mouse button triggered pointer events (left, right, middle, etc.) and registers missing W3C pointer event handlers: Add button property mouse events (#15819)

Reliability

Circular dependency build issues for RNW Fabric App fixed: Fix Circular Dependency issues for New Arch Apps (#15747)
Update WinAppSdk to 1.8.260209005: Update WinAppSdk to 1.8.260209005 (#15660)
Fix init-windows C++ codegen include to use codegenConfig.name: Fix init-windows C++ codegen include to use codegenConfig.name(#15619)
Fix XAML popup positioning and light dismiss in ScrollView: Fix XAML popup positioning and light dismiss in ScrollView(#15564)
Fix TextInput selection crash and feedback loop: Fix TextInput selection prop (#15672)
Fixed SHIFT+F10 keyboard shortcut not showing context menu in TextInput components: Fix SHIFT+F10 keyboard shortcut for context menu in TextInput (#15621)
Adding defensive check to ensure device context is valid before D2D operations: adding defensive check to ensure device context is valid before D2D operations (#15620)
Fixed issue where box with corner radius doesn't have shadow: Fixing box with corner radius doesn't have shadow (#15613)
Bring Narrator focus to the XAML island for community module native components: Bring Narrator focus to XAML island (#15611)
Fixed selectable text not receiving pointer events inside ScrollView: Fix selectable text not receiving pointer events inside ScrollView (#15577)
Fixed detection of projects with mixed architecture support: fix(cli): fix template info not detecting mixed architecture projects (#15567)
Fixed a silent MSBuild linker bug in the cpp-app and cpp-lib templates where a typo in %(AdditionalDependencies) caused inherited link dependencies to be silently dropped: fix: %(AdditionalDependencies) metadata typo in cpp-app/cpp-lib templates and package projects (#15720)