CVE-2026-73489: Russh: Post-auth remote panic via pty-req with more than 130 terminal-mode records

Russh is a Rust SSH client & server library. Prior to 0.62.4, an authenticated SSH client can cause a denial of service by sending a pty-req channel request with more than 130 terminal-mode records. The parser in russh/src/server/encrypted.rs stores terminal modes in a fixed 130-entry [(Pty::TTYOPEND, 0); 130] array but continues increasing the mode count, then constructs an out-of-bounds slice and panics before the application ptyrequest handler runs. The panic terminates the server session task without causing memory corruption. This issue is fixed in version 0.62.4.