Changes

• Add support for formatter temp file configuration in 462e2e8

  Support formatters that read/write files instead of stdin/stdout by
  adding new formatter config options (stdout, file_ext, and
  colocate_temp_file) and threading a source file path through
  formatting calls.

  Also add --stdin-filepath to associate stdin content with a path,
  improve temp file naming/location behavior for non-stdin formatters, and
  expand tests to cover the new config parsing and temp-file behavior.

• Print diffs for dirty files in check mode in a895bd4

  If a file is dirty when running with --check=true, print a unified
  diff to stderr so the formatting changes are visible without modifying
  files.

  This adds a dedicated api::diff module for diff generation and
  colorized rendering, and wires check-mode file processing to emit diffs
  as dirty files are discovered.

Full Changelog: v1.0.0-alpha.9...v1.0.0-alpha.10