Add lib.c and hvm_lib.h for embedding HVM as a library

[lancejpollard]

Summary

Adds clang/lib.c and clang/hvm_lib.h so HVM can be compiled as a static or shared library for embedding in other applications.

Since hvm.c uses #define fn static inline, all functions are private. lib.c includes hvm.c and provides non-static wrapper functions that create real linker symbols, following the same single-TU pattern as main.c.

All exported symbols use an hvm_ prefix to avoid name collisions when linked into a host application.

Benefits

• Enables embedding. Without this, HVM can only be used via the CLI. With lib.c, it can be linked into any C, Rust, Swift, or Kotlin project as a library.
• Zero architecture change. Follows the same #include "hvm.c" pattern that main.c already uses. No refactoring of the core. The thin wrappers inline away at -O2, so there is no performance cost.
• Namespaced symbols. The hvm_ prefix prevents collisions when linked into larger applications that may have their own init, free, etc.
• Supports all targets. The same lib.c compiles for macOS, Linux, iOS (static), Android (shared), and WASM (via emcc). One source file for all platforms.
• Stable public API. hvm_lib.h gives consumers a versioned header to code against, decoupled from internal function names that may change upstream.

Usage

# Static library
clang -O2 -c lib.c -o hvm.o
ar rcs libhvm.a hvm.o

# Shared library (macOS)
clang -O2 -dynamiclib lib.c -o libhvm.dylib

# Shared library (Linux)
clang -O2 -shared -fPIC lib.c -o libhvm.so -ldl

#include "hvm_lib.h"

int main(void) {
  hvm_init(1, 0, 0, 0);

  u32 main_id;
  char src[] = "@main = 42";
  if (hvm_prepare(&main_id, "inline", src)) {
    Term ref  = hvm_term_new_ref(main_id);
    Term norm = hvm_wnf(ref);
    // use norm...
  }

  hvm_free();
  return 0;
}

Exported API

Category	Functions
Lifecycle	hvm_init, hvm_free, hvm_prepare, hvm_prepare_text
Evaluation	hvm_wnf, hvm_normalize
Constructors	hvm_term_new_{num,ctr,sup,dup,app,lam,lam_at,var,ref}
Accessors	hvm_term_{tag,ext,val}
Heap	hvm_heap_{read,set,alloc}
Table	hvm_table_find
Primitives	hvm_prim_register