Expose selection endpoint ordering through the libghostty-vt C API so
embedders can safely normalize selections whose start and end refs may be
reversed. The new APIs report the current order and return a fresh
untracked selection with forward or reverse bounds.
Selection.Order now uses lib.Enum, matching the existing adjustment enum
pattern and keeping the C ABI enum generated from the same Zig source of
truth. The new functions are wired through the C API re-export and lib-vt
export paths, with coverage for mirrored rectangular selection ordering.
Clarify that GhosttySelection is a snapshot type whose endpoints are
untracked GhosttyGridRef values. The previous documentation described the
range shape but did not repeat the grid reference lifetime caveat, which
made it easy to keep selections across terminal mutations incorrectly.
Add a new GhosttySelection C API type (selection.h / c/selection.zig)
that pairs two GhosttyGridRef endpoints with a rectangle flag. This
maps directly to the internal Selection type using untracked pins.
The formatter terminal options gain an optional selection pointer.
When non-null the formatter restricts output to the specified range
instead of emitting the entire screen. When null the existing
behavior of formatting the full screen is preserved.
Mitchell Hashimoto