In @.changeset/silver-sites-taste.md:
- Line 5: Update the changeset note that starts with "Fixed
[](https://github.com/biomejs/biome/issues/9090), where SCSS files were
incorrectly processed by Biome." — change "a regressions" to "a regression" and
slightly rephrase the clause to read smoothly (for example: "This was a
regression caused by recent changes to SCSS support" or similar) so the sentence
is grammatically correct and clearer.

In `@crates/biome_cli/tests/commands/format.rs`:
- Around line 4037-4055: The test harness_scss currently asserts only
result.is_err() and has a typo in the failure message; update it to (1) fix the
typo in the assertion message and (2) assert the error or console output
contains the expected SCSS-unsupported message to lock behavior: capture the
error via result.unwrap_err() (or format the console buffer from BufferConsole)
and assert it contains a stable substring like "SCSS support is not available"
(or the real message returned by run_cli/Args), or replace the ad-hoc check with
a snapshot/assert_eq against the expected output to prevent regressions;
reference harness_scss, run_cli, Args, BufferConsole, and MemoryFileSystem when
locating and making this change.