Repo: dotnet/sdk (owner: dotnet)

Please create a pull request that fixes only the second step/checkbox described in issue #52775.

Scope constraints:

• Implement only the second step from the issue.
• Do not implement or partially implement the third step (leave it for later).

What to do (second step):

• Fix the license headers for the dotnet-format code.
• After license headers are corrected, remove the exclusion in .editorconfig for src/tests that was excluding those test sources (the exclusion was presumably present to avoid license-header enforcement failures).

Acceptance criteria:

• dotnet-format code under this repository has correct license headers per repo conventions.
• .editorconfig no longer excludes src/tests for the relevant analyzer/license-header rule(s), while keeping any unrelated exclusions intact.
• The change set is limited to what’s necessary for the second step; avoid touching unrelated formatting/whitespace and avoid any work related to the third step in the issue.
• PR should include a clear description referencing issue File license header is not enforced in all source code #52775 and explicitly stating it completes only step 2.

Notes:

• Determine the repo’s expected license header text/pattern and apply it consistently to applicable dotnet-format source files.
• Update tests under src/tests as needed so that removing the .editorconfig exclusion does not reintroduce failures, but keep changes minimal.