[agustux]

Fixes #20

main.c passed &medium_enabled (a bool*) to
GHOSTTY_TERMINAL_OPT_KITTY_IMAGE_MEDIUM_TEMP_FILE, but that option
takes a GhosttyString* (the directory the temp-file medium is
restricted to; NULL disables it). MEDIUM_FILE and MEDIUM_SHARED_MEM
do take bool*, so the shared variable hid the mismatch.

Debug builds panic at startup with "incorrect alignment" in
ghostty_terminal_set, because the library casts the 1-byte bool to
GhosttyString*. In Release builds the library reads a GhosttyString
from a 1-byte object, which is undefined behavior.

This passes a GhosttyString for /tmp to the temp-file option. The
string is copied into the terminal, so a literal is safe. The bool*
options are unchanged, and comments explain the type difference, per
AGENTS.md. The change is limited to main.c; CMakeLists.txt and
libghostty are untouched.

Tested:

• cmake -B build-dbg -G Ninja -DCMAKE_BUILD_TYPE=Debug then
  cmake --build build-dbg && ./build-dbg/ghostling (Debug) launches
  with no panic. It panicked at main.c:1351 before this change.

Note: We can change /tmp if you'd prefer $TMPDIR to be a different default.

Note: building currently hangs on bin2header.cmake (#16` fixed in #19 ). I tested on top of that fix.