v0.7.4-alpha — terminal paste fixed, configurable scrollback

Two terminal fixes.

Fixed

Pasting a multi-line block into a terminal mangled it. Newlines were sent as LF
(0x0A). The Enter key sends CR (0x0D), and the tty turns that into a newline for the
application — LF instead arrives as a literal ^J, and in nano ^J is the Justify
command. Pasting a certificate therefore ran justify on every line and came back reflowed
into two columns.

Both paste paths were affected: right-click bypassed the terminal's own handling entirely,
and Cmd+V does wrap the text in bracketed-paste markers but never converted line endings,
so it broke the same way whenever the remote application hadn't enabled that mode.

Paste now converts CRLF/LF to CR and wraps the run in bracketed-paste markers when the
terminal reports that mode, so editors insert it literally instead of interpreting it as
typing — no command interpretation, no auto-indent stair-stepping.

New

Scrollback is configurable — Settings → Terminal scrollback: 1 000 / 5 000 / 10 000 /
25 000 / 50 000 / 100 000 lines, defaulting to 10 000. It used to be fixed at 500, so
anything longer than a screenful or two lost its top with no way to scroll back. A change
applies to tabs that are already open, not just new ones.