Echo typed input in interactive ghostel-compile runs - #591

Problem

Interactive input worked in ghostel-compile buffers, but typed characters never appeared: the PTY was always spawned with -echo, and the C-c C-j toggle (ghostel-compile-switch-to-interactive) only swapped keymaps without touching termios. Typing at a read-style prompt was invisible.

Fix

• Interactive spawns (C-u M-x ghostel-compile) configure the PTY with ghostel--default-stty (echo on), so input is visible from the first keystroke.
• The mid-run toggle flips ECHO out-of-band on the live PTY via stty against process-tty-name (Emacs has no termios API). Local runs only — for TRAMP the process tty is the local connection pty, not the remote pty the command reads from.
• The enable is skipped when:
  • the tty is in non-canonical mode — a full-screen program (htop, less) owns the display and echoed keystrokes would splatter over it;
  • the cursor row matches ghostel-password-prompt-regex — the pty state cannot distinguish a program-set -echo (ssh, sudo, read -s) from the compile spawn default, but the prompt text can. Typed secrets must not render into the buffer.
• Compilation-style runs keep -echo: the buffer is a pure log, and echoed terminal query replies (DA1, DSR, OSC color reports) would render as escape-sequence garbage.

Known residual: a password prompt whose text doesn't match the regex and is already on screen at toggle time gets echoed — the same residual every comint-based mode has.

Tests

Four new native tests: interactive spawn echoes typed input before the program responds (the script blocks in read, so the text can only come from tty echo), the toggle enables echo mid-run, the raw-mode guard leaves a TUI's terminal alone, and a Password: prompt keeps ECHO off across the toggle. Test markers are assembled from printf fragments so the command line echoed in the buffer header can't satisfy the wait predicates.

Verified live in a TTY Emacs: typed input echoes at the prompt (including DEL erase), and typing at a password prompt after C-c C-j renders nothing while still reaching the program.