Add .NET 11 breaking change: restore doesn't search the global packages folder for a higher package version

[Copilot]

In .NET 11 RC 1, when a requested package version doesn't exist, NuGet restore only searches package sources for the "next best" (lowest higher) version — versions present only in the global packages folder are no longer candidates. This can change which version is selected, or turn an NU1603 warning into an NU1102 error.

Changes

• New article docs/core/compatibility/sdk/11/restore-global-packages-folder-version-search.md — previous/new behavior tables adapted from the issue, the unchanged exact-version-match carve-out, reason (determinism across machines), and recommended action linking to NuGet supply-chain best practices.
• TOC — entry added under SDK and MSBuild (.NET 11) in docs/core/compatibility/toc.yml.
• Index — row added to the SDK and MSBuild table in docs/core/compatibility/11.md.

Notes for reviewers

• The issue text uses NU1604 in the tables but NU1603 in the prose; the article uses NU1603 throughout, since NU1603 is the "resolved to a higher version than requested" warning and NU1604 is the "dependency without a lower bound" warning. Please confirm.
• Type of change follows the issue's selection: Source incompatible (restore can now fail with NU1102). Automated review suggested "Behavioral change" — flagging in case the SDK team prefers that categorization; the article and index entry currently match each other.
• No other articles in this repo document the NU1603/NU1102 fallback behavior (that content lives in the NuGet docs repo), so no related-article updates were made.

• Fixes [Breaking change]: Restore will no longer search package versions from the global packages folder when choosing a higher version #55108

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Internal previews

File	Preview link
docs/core/compatibility/11.md	Learn preview
docs/core/compatibility/sdk/11/restore-global-packages-folder-version-search.md	Learn preview
docs/core/compatibility/toc.yml	Learn preview

Build report

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[BillWagner]

This LGTM.