cli: add --gpu <index> to select a Vulkan physical deviceFeature gpu select (#417)

* cli: add --gpu <index> to select a Vulkan physical device

Select the Vulkan physical device by enumeration index, defaulting to
automatic selection (-1). Invalid or out-of-range indices fall back to
automatic selection with a clear message, and the selected device is
logged.

Co-Authored-By: Claude <noreply@anthropic.com>

* cli: reject invalid --gpu index, translate comments, apply clang-format

An invalid --gpu index now prints an error and exits with code 1 (usage),
matching --user-id / --present-mode / --console-language. The automatic
fallback is kept only for out-of-range indices detected at runtime.
Comments translated to English and the touched files brought in line
with clang-format (pre-commit v22.1.3).

Co-Authored-By: Claude <noreply@anthropic.com>

* cli: simplify Vulkan device selection

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: nmzik <Nmzik@mail.ru>

src/main.cpp

@@ -52,6 +52,8 @@ static void PrintUsage() {
 	         Config::DEFAULT_USER_ID);
 	::printf(
 	    "  --present-mode <value>               Fifo, Mailbox, or Immediate. Default: Fifo.\n");
+	::printf(
+	    "  --gpu <index>                        Vulkan physical device index. Default: auto.\n");
 	::printf("  --fullscreen                         Run in borderless desktop fullscreen.\n");
 	::printf("  --vblank-frequency <num>             Virtual vblank frequency. Default: 60.\n");
 	::printf("  --console-language <0-29>            Console language. Default: 1 (English US).\n");
@@ -234,6 +236,8 @@ static bool ParseArgs(int argc, char* argv[], RunOptions& options, bool& show_he
 				::printf("invalid present mode: %s\n", value.c_str());
 				return false;
 			}
+		} else if (arg == "--gpu") {
+			options.config.gpu_index = Common::ToInt32(value);
 		} else if (arg == "--vblank-frequency") {
 			const int32_t vblank_frequency = Common::ToInt32(value);
 			options.config.vblank_frequency =