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/README.md

@@ -0,0 +1,45 @@
+# originclient (Go)
+
+```
+go get git.warky.dev/wdevs/origin_client/go
+```
+
+## Usage
+
+```go
+c, err := originclient.New(originclient.Config{
+    ServiceKey: "...",
+    Type:       "myservice",
+    Version:    "1.2.3",
+    Name:       "myservice-nova",
+})
+if err != nil {
+    log.Fatal(err)
+}
+go c.Run(ctx) // immediate check-in, then every 24h until ctx is done
+```
+
+Call `c.CheckinOnce(ctx)` directly instead of `Run` to send a single
+check-in and observe the error/response.
+
+## Config
+
+| Field | Required | Default |
+|---|---|---|
+| `ServiceKey` | yes | — |
+| `Type`, `Version`, `Name` | yes | — |
+| `URL` | no | `DefaultURL` (`https://origin.warky.dev/api/public/service-checkin`) |
+| `AppType` | no | `"go"` |
+| `Hostname` | no | OS hostname |
+| `ContainerID` | no | best-effort Docker/cgroup detection |
+| `Orchestrator` | no | best-effort Kubernetes/Docker detection |
+| `InstallID` | no | OS machine ID, else a generated UUID persisted to `InstallIDPath` |
+| `IntervalHours` | no | `DefaultIntervalHours` (24) |
+| `Logger` | no | discards warnings |
+
+`Site`, `Environment`, `DatabaseType`, `DatabaseName`, `Port`, `BaseURL`,
+`InternalURL`, `Description` are optional metadata with no default.
+
+`Hostname()`, `OutboundIP()`, `ContainerID()`, `Orchestrator()`, and
+`ResolveMachineID()` are exported standalone for callers that want the
+detection logic without the HTTP client.