Terminal construction previously accepted GhosttyTerminalOptions with
dimensions and one scrollback byte limit. Remove the options struct from
the ABI and make ghostty_terminal_new accept columns and rows directly.
Add byte and line limit options to ghostty_terminal_set and forward them
to the runtime Terminal setters. NULL removes a limit, while zero bytes
disables scrollback. Update type metadata, tests, and all API examples.
Add a ghostty_vt_add_target() CMake function that lets downstream
projects build libghostty-vt for a specific Zig target triple. The
function encapsulates zig discovery, build-type-to-optimize mapping,
the zig build invocation, and output path conventions so consumers
do not need to duplicate any of that logic. It creates named IMPORTED
targets (e.g. ghostty-vt-static-linux-amd64) that work alongside the
existing native ghostty-vt and ghostty-vt-static targets.
The build-type mapping is factored into a shared _GHOSTTY_ZIG_OPT_FLAG
variable used by both the native build and the new function.
The static library targets now propagate c++ as a link dependency on
non-Windows platforms, fixing link failures when consumers use static
linking with the default SIMD-enabled build.
A new example/c-vt-cmake-cross/ demonstrates end-to-end cross-
compilation using zig cc as the C compiler, auto-detecting a cross
target based on the host OS.
