Show site uptime

Returns the site's uptime summary as a meta-only JSON:API document (a computed structure, not a resource): whether uptime is `configured` and `enabled`, the current `status` (`up` / `down` / `unknown`) with `status_since`, the `last_ping` (`at`, `status`, `status_code`, `response_time_ms`, `error`) and rolling `availability` windows — `day`, `week` and `month` — each with an uptime `percentage` and `total_pings`. Sites without an uptime service answer `configured: false` with everything else null. A paused service reports `status: "unknown"` but keeps historical `last_ping` / `availability`. A window with no pings reports `percentage: null`, never a fake 100. This read is heavier than `Show site` (it runs availability stats queries per call) — fetch it for the site you are inspecting, not in a loop over your whole site list. Sites of other organizations answer 404. The MCP twin of this endpoint is the `sites-uptime-show` tool.