v0.9.1 — fix darnlink check crash on Windows cp1252

Fix: darnlink check no longer crashes on a Windows cp1252 console.

The summary line printed → (U+2192), which the Spanish-Windows default code page (cp1252) cannot encode → UnicodeEncodeError → the gate exited non-zero on encoding, not on links (a false red for every Windows repo running the gate). The arrow is now ASCII ->, and main() makes stdout/stderr degrade unencodable output instead of raising — so the gate can never crash on a console encoding again. No PYTHONUTF8 workaround needed.

Regression test asserts the check output is cp1252-encodable.