fix(ffi): remove duplicate proven_free_string export

Author: hyperpolymath

ffi/zig/src/main.zig

@@ -88,14 +88,6 @@ export fn proven_version_patch() u32 { return 0; }
 /// Return the FFI ABI version
 export fn proven_ffi_abi_version() u32 { return 1; }
 
-/// Free a string allocated by the library
-export fn proven_free_string(ptr: ?[*]const u8) void {
-    const p = ptr orelse return;
-    // Find the null terminator to determine length for the allocator
-    const len = std.mem.len(p);
-    std.heap.c_allocator.free(p[0..len + 1]);
-}
-
 //==============================================================================
 // Core Operations
 //==============================================================================