v0.7.1

fix(v0.7.1): local echo for Windows terminal (no-PTY shell)

cmd.exe spawned with raw pipes (no ConPTY) does not echo typed
characters back, so users saw no visual feedback as they typed. Diag
strip confirmed input was reaching server WS but display stayed blank.

Server now flags Windows shells as shellNoPty and the writeShell() path
fakes echo by sending the keystrokes back as terminal.data:
  - regular printable chars echoed as-is
  - \r (Enter) echoed as \r\n; \r\n also sent to cmd.exe stdin
    so it executes the line
  - \x7f (Backspace) echoed as the BS/space/BS triple, sent as \b
    so cmd.exe also erases from its line buffer

Linux/macOS retain real PTY echo via script(1) wrapping — unchanged.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>