feat(python): support Ruff formatting and config directories (#1573)

Ruff is now an external formatter for Python next to the Ruff language server: Settings › Languages & Frameworks › Ruff has the executable path, a configuration directory (or file), the provider preference, enabled languages, run-on-save, and Reformat with Ruff. Formatting runs on the unsaved document through stdin (with Ruff's --range for selections, in 1-based code-point columns) and never writes the file first. The configuration directory is shared with Ruff LSP, which can then start without a root marker. Tools that can't format a language are rejected even when requested.

Co-authored-by: muutot <[email protected]>
Co-Authored-By: Claude Opus 5.5 <[email protected]>

languages/python.toml

@@ -1,5 +1,6 @@
 id = "python"
 name = "Python"
+formatter = { tool = "ruff", parser = "python", range = true }
 extensions = ["py", "pyi", "pyw"]
 filenames = ["SConstruct", "SConscript"]
 first-line = "^#!.*\\bpython[0-9.]*\\b"