build: add cmake static library support

Expose both shared and static libraries as separate CMake imported
targets (ghostty-vt and ghostty-vt-static) rather than toggling
between them with BUILD_SHARED_LIBS. The zig build already produces
both in a single invocation, so both are always available.

The find_package config template is updated to export both targets
as ghostty-vt::ghostty-vt and ghostty-vt::ghostty-vt-static.

Add a c-vt-cmake-static example that demonstrates linking the static
library via FetchContent with -Dsimd=false to avoid C++ runtime
dependencies.

example/c-vt-cmake-static/CMakeLists.txt

@@ -0,0 +1,13 @@
+cmake_minimum_required(VERSION 3.19)
+project(c-vt-cmake-static LANGUAGES C)
+
+include(FetchContent)
+FetchContent_Declare(ghostty
+    GIT_REPOSITORY https://github.com/ghostty-org/ghostty.git
+    GIT_TAG main
+)
+set(GHOSTTY_ZIG_BUILD_FLAGS "-Dsimd=false" CACHE STRING "" FORCE)
+FetchContent_MakeAvailable(ghostty)
+
+add_executable(c_vt_cmake_static src/main.c)
+target_link_libraries(c_vt_cmake_static PRIVATE ghostty-vt-static)

example/c-vt-cmake-static/README.md

@@ -0,0 +1,21 @@
+# c-vt-cmake-static
+
+Demonstrates consuming libghostty-vt as a **static** library from a CMake
+project using `FetchContent`. Creates a terminal, writes VT sequences into
+it, and formats the screen contents as plain text.
+
+## Building
+
+```shell-session
+cd example/c-vt-cmake-static
+cmake -B build
+cmake --build build
+./build/c_vt_cmake_static
+```
+
+To build against a local checkout instead of fetching from GitHub:
+
+```shell-session
+cmake -B build -DFETCHCONTENT_SOURCE_DIR_GHOSTTY=../..
+cmake --build build
+```

example/c-vt-cmake-static/src/main.c

@@ -0,0 +1,52 @@
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ghostty/vt.h>
+
+int main() {
+  // Create a terminal with a small grid
+  GhosttyTerminal terminal;
+  GhosttyTerminalOptions opts = {
+    .cols = 80,
+    .rows = 24,
+    .max_scrollback = 0,
+  };
+  GhosttyResult result = ghostty_terminal_new(NULL, &terminal, opts);
+  assert(result == GHOSTTY_SUCCESS);
+
+  // Write some VT-encoded content into the terminal
+  const char *commands[] = {
+    "Hello from a \033[1mCMake\033[0m-built program (static)!\r\n",
+    "Line 2: \033[4munderlined\033[0m text\r\n",
+    "Line 3: \033[31mred\033[0m \033[32mgreen\033[0m \033[34mblue\033[0m\r\n",
+  };
+  for (size_t i = 0; i < sizeof(commands) / sizeof(commands[0]); i++) {
+    ghostty_terminal_vt_write(terminal, (const uint8_t *)commands[i],
+                              strlen(commands[i]));
+  }
+
+  // Format the terminal contents as plain text
+  GhosttyFormatterTerminalOptions fmt_opts =
+      GHOSTTY_INIT_SIZED(GhosttyFormatterTerminalOptions);
+  fmt_opts.emit = GHOSTTY_FORMATTER_FORMAT_PLAIN;
+  fmt_opts.trim = true;
+
+  GhosttyFormatter formatter;
+  result = ghostty_formatter_terminal_new(NULL, &formatter, terminal, fmt_opts);
+  assert(result == GHOSTTY_SUCCESS);
+
+  uint8_t *buf = NULL;
+  size_t len = 0;
+  result = ghostty_formatter_format_alloc(formatter, NULL, &buf, &len);
+  assert(result == GHOSTTY_SUCCESS);
+
+  printf("Plain text (%zu bytes):\n", len);
+  fwrite(buf, 1, len, stdout);
+  printf("\n");
+
+  free(buf);
+  ghostty_formatter_free(formatter);
+  ghostty_terminal_free(terminal);
+  return 0;
+}