Translate user-facing runtime output to English, machine prefixes preserved, + CLI output test (#67, #85)

* feat: standardize runtime output in English

* test: cover English CLI output

c/tools/gen_unicode.py

@@ -41,7 +41,7 @@ def emit(name, rs):
     print("};")
     print(f"static const int {name}_n = {len(rs)};\n")
 
-print("/* GENERATO da tools/gen_unicode.py — non modificare a mano. */")
+print("/* GENERATED by tools/gen_unicode.py — do not edit by hand. */")
 print("#ifndef TOK_UNICODE_H\n#define TOK_UNICODE_H\n#include <stdint.h>\n")
 emit("uni_L", L); emit("uni_N", N); emit("uni_S", S)
 print("""static int uni_in(const uint32_t t[][2], int n, uint32_t cp){