blur variants

// Test 818: Parsing |variant syntax
//
// Tests that the parser recognizes and accepts |variant syntax.
// This is the FIRST test using |variant (previous tests used :target).
//
// What this tests:
// ✅ Parser accepts blur|naive syntax
// ✅ Parser accepts blur|gpu syntax
// ✅ Both procs emit correctly
//
// What this does NOT test:
// ❌ Actual polyglot compilation (not implemented yet)
// ❌ Variant selection logic (future work)
// ❌ GPU code generation (future work)

~pub event blur { }
| done { }

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

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