feat: initial Go/JS/Rust Origin check-in client SDKs

Standalone clients that resolve a machine unique ID (OS machine ID first,
falling back to a generated UUID persisted to disk), detect hostname/IP/
container/orchestrator, and register+re-ping origin.warky.dev's public
service-checkin endpoint on a daily interval. Ported from icy2's internal
origincheckin package but extended to the full check-in contract and made
dependency-light for external reuse.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

go/logger.go

@@ -0,0 +1,20 @@
+package originclient
+
+// Logger receives non-fatal warnings from the client (encode/build/request
+// failures, machine-id/persistence fallbacks). It intentionally mirrors the
+// smallest common subset of structured loggers so callers can adapt zap,
+// slog, logrus, or anything else with one line.
+type Logger interface {
+	Warn(msg string, err error)
+}
+
+// LoggerFunc adapts a function to Logger.
+type LoggerFunc func(msg string, err error)
+
+// Warn implements Logger.
+func (f LoggerFunc) Warn(msg string, err error) { f(msg, err) }
+
+// noopLogger discards every warning.
+type noopLogger struct{}
+
+func (noopLogger) Warn(string, error) {}