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>

README.md

@@ -1,3 +1,44 @@
 # origin_client
 
-origin client
+Client SDKs that register a running service with
+[Origin](https://origin.warky.dev)'s public check-in endpoint and re-ping it
+on an interval. One package per language, same wire contract, same behavior.
+
+## Packages
+
+| Language | Path | Module/package |
+|---|---|---|
+| Go | [`go/`](go/) | `git.warky.dev/wdevs/origin_client/go` |
+| JavaScript/TypeScript | [`js/`](js/) | `@warkanum/origin-client` |
+| Rust | [`rust/`](rust/) | `origin-client` |
+
+## What it does
+
+- Resolves a machine unique ID: real OS ID first (`/etc/machine-id` on
+  Linux, `IOPlatformUUID` on macOS, `MachineGuid` on Windows), falling back
+  to a generated UUID persisted to disk.
+- Detects hostname, outbound IP, container ID (Docker/cgroup), and
+  orchestrator (Kubernetes/Docker) best-effort.
+- POSTs a check-in payload to Origin immediately, then again every
+  `interval_hours` (default 24), until stopped. Network/server failures are
+  logged and swallowed — check-in never crashes or blocks the host app.
+
+## Wire contract
+
+`POST {base_url}` (default `https://origin.warky.dev/api/public/service-checkin`)
+with header `X-Origin-Service-Key: <your key>`.
+
+Required: `type`, `version`, `name`, `unique_install_id`.
+Optional: `site`, `environment`, `database_type`, `database_name`,
+`app_type`, `hostname`, `port`, `base_url`, `internal_url`, `container_id`,
+`orchestrator`, `description`.
+
+Response: `success`, `service_instance_id`, `unique_install_id`, `status`,
+`pinged_at`.
+
+Full contract: see `origin/doc/service-checkin.md` in the Origin repo.
+
+## Status
+
+Structured for independent versioning/publishing per package. Not yet
+published to any registry.