Terminal: send Shift+Tab, Delete, Ctrl+Alt and Ctrl+digit keys as xterm does - #3067

Keys that Claude Code, Codex and other terminal programs use, checked key by key against xterm:

• Shift+Tab sends back tab (CSI Z), as xterm and Windows Terminal do, and no longer moves the focus out of the terminal; Claude Code switches modes with it.
• Ctrl, Shift and Alt with Delete carry the modifier (CSI 3 ; 5 ~ and so on); every Delete used to arrive as a plain Delete.
• A real Ctrl+Alt keeps its Alt: ESC before the control character, as in xterm (Ctrl+Alt+V pastes an image in Codex on WSL). AltGr, which SWT reports as Ctrl+Alt with the character it types, types that character as before.
• Ctrl+2 to Ctrl+8 send NUL, ESC, FS, GS, RS, US and DEL; on Windows they sent the digits.
• On the alternate screen Alt and Ctrl with the arrows go to the full screen program even where Eclipse has a binding for them (Alt+Up edits a queued message in Codex); at the shell prompt Alt+Up still maximizes the view.

How to test, in a bash terminal: run od -c, press the key, then Enter, and Ctrl+D to end.

• Shift+Tab shows 033 [ Z, and the focus stays in the terminal.
• Ctrl+Delete shows 033 [ 3 ; 5 ~ (Shift: ; 2, Alt: ; 3).
• Ctrl+Alt+V shows 033 026; on a German keyboard AltGr+Q still types @.
• Ctrl+6 shows 036.
• In vim (alternate screen) Alt+Up is not taken by Eclipse; at the prompt Alt+Up still maximizes the view.

Tests: new cases in VT100EmulatorTest for Ctrl with the digits, Alt with ESC (AltGr included), Delete with modifiers and the alternate screen flag.