By: Tom Sydney Kerckhove <syd@cs-syd.eu>
Add OscSequence token to parse and discard OSC escape sequences GHC emits OSC 8 hyperlink sequences in warning messages (e.g. for error code documentation URLs). These begin with ESC ] and end with the String Terminator (ESC \) or BEL. The tokenizer previously only handled CSI sequences (ESC [), so OSC bytes leaked through as plain text. Add OscSequence to AnsiToken, oscSequenceP to the tokenizer, and handle it as a discard in tokensToChunks. Update stripAnsi in the test helper to also strip OSC sequences so the concatenation property test remains valid.