051 build variants

// Test: build:variants populates variant registry based on --build flag
// When --build=release, the release config should be used
// When --build=debug, the debug config should be used

~import "$std/io"
~import "$std/build"

// Define events that we'll configure variants for
~event compute { x: i32 }
| done { result: i32 }

~proc compute {
    return .{ .done = .{ .result = x } };
}

~proc compute|fast {
    return .{ .done = .{ .result = x * 2 } };
}

~proc compute|naive {
    return .{ .done = .{ .result = x } };
}

~event blur { intensity: i32 }
| done {}

~proc blur {
    return .{ .done = .{} };
}

~proc blur|gpu {
    return .{ .done = .{} };
}

~proc blur|cpu {
    return .{ .done = .{} };
}

// Define variant configurations for different build modes
// Use full canonical names: module:event
~[release]std.build:variants {
    "input:compute": "fast",
    "input:blur": "gpu"
}
| configured _ |> std.io:println(text: "Release config loaded")
| skipped _ |> _
| invalid_event _ |> std.io:println(text: "Invalid event in release config")

~[debug]std.build:variants {
    "input:compute": "naive",
    "input:blur": "cpu"
}
| configured _ |> std.io:println(text: "Debug config loaded")
| skipped _ |> _
| invalid_event _ |> std.io:println(text: "Invalid event in debug config")

// Default config (when no --build flag is passed)
~std.build:variants {
    "input:compute": "default",
    "input:blur": "default"
}
| configured _ |> std.io:println(text: "Default config loaded")
| skipped _ |> _
| invalid_event _ |> std.io:println(text: "Invalid event in default config")