Function should_emit_conemu94 

pub fn should_emit_conemu94(
    windows_terminal: bool,
    conemu: bool,
    ghostty_supported: bool,
) -> bool

Pure gate: OSC 9;4 renders only on terminals documented to honor it.

Everywhere else OSC 9 may mean notifications (iTerm2, older Ghostty), so this is default-deny: unknown terminals never receive the sequence.