docs: clarify global.json search logic for muxer vs MSBuild SDK resolver (#52097)

* Initial plan

* Update global.json docs to clarify muxer vs MSBuild SDK resolver search logic

Co-authored-by: meaghanlewis <10103121+meaghanlewis@users.noreply.github.com>

* Update docs/core/tools/global-json.md

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: meaghanlewis <10103121+meaghanlewis@users.noreply.github.com>
Co-authored-by: Meaghan Osagie (Lewis) <mosagie@microsoft.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: 3 people

docs/core/tools/global-json.md

@@ -2,7 +2,7 @@
 title: global.json overview
 description: Learn how to use the global.json file to set the .NET SDK version when running .NET CLI commands.
 ms.topic: how-to
-ms.date: 10/22/2025
+ms.date: 03/05/2026
 ms.custom: "updateeachrelease"
 ai-usage: ai-assisted
 ---
@@ -23,7 +23,10 @@ If you always want to use the latest SDK version that is installed on your machi
 }
 ```
 
-The .NET SDK looks for a *global.json* file in the current working directory (which isn't necessarily the same as the project directory) or one of its ancestor directories.
+You rely on two components in the .NET SDK to search for a *global.json* file. Each component starts from a different location and searches up through ancestor directories:
+
+- **.NET SDK muxer** handles `dotnet` CLI commands. It starts from the current working directory, which isn't necessarily the same as the project directory.
+- **.NET MSBuild project SDK resolver** resolves project SDKs during builds. It starts from the directory that contains a solution file, if one exists. If no solution file exists, it starts from the directory that contains the current project file. If neither file exists, it uses the current working directory.
 
 For information about specifying the runtime version instead of the SDK version, see [Target frameworks](../../standard/frameworks.md).