finch.toml, threads and atomics, finch fmt, C++ files, struct #defines, a struct variable given for its ptr

- finch.toml: name, entry, paths, include, links, libdirs, cflags, ldflags, and [target.windows] etc.;
  finch run / build / test with no file use its entry
- import thread: spawn, join, mutex, cpus; atomic_add/sub/load/store/swap/cas built in
- finch fmt [--check]: indentation by { }, trailing spaces, empty lines; also as LSP formatting
- link "x.cpp" (or in finch.toml): built with the C++ compiler, which then links (FINCH_CXX)
- #define RAYWHITE (Color){ 245, 245, 245, 255 } imports as a Color
- push(body) where push takes ptr[Body]: the same as push(addr(body))
- --target android (NDK clang from ANDROID_NDK_HOME, -llog)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016GzNP6r8dg6WDxUVZy8wjL

std/finch_thread.h

@@ -0,0 +1,8 @@
+/* The runtime's thread functions, for std/thread.fch (they are in runtime/finch_rt.c, linked into every program). */
+void *finch_thread_spawn(void (*fn)(void *), void *arg);
+int finch_thread_join(void *thread);
+void *finch_mutex_new(void);
+void finch_mutex_lock(void *mutex);
+void finch_mutex_unlock(void *mutex);
+void finch_mutex_free(void *mutex);
+int finch_cpu_count(void);