#1971 docs: add self-hosting guide (fixes 404 from agentrelay.com)

Summary

• Adds docs/self-hosting/README.md, the target of agentrelay.com's homepage "Self host" card, which currently 404s.
• Uses Relaycast's self-hosting guide as the engine reference, then documents how Agent Relay targets a self-hosted origin: RELAY_BASE_URL / RELAYCAST_BASE_URL (broker precedence), RELAYCAST_WS_URL, RELAY_API_KEY, broker forwarding to workers, and the SDK baseUrl.
• Links the guide from the root README's Self Hosting section.

Docs-only, so no changelog entry.

🤖 Generated with Claude Code

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[!NOTE]
Low Risk
Documentation-only changes with no runtime, auth, or data-path modifications.

Overview
Adds docs/self-hosting/README.md so the site’s “Self host” entry has a real target (previously 404). The guide maps Relaycast, broker/CLI, and optional Relayfile, points operators at Relaycast’s upstream self-hosting doc, and explains how to aim agent-relay node up at a private engine via RELAY_BASE_URL / RELAYCAST_BASE_URL, workspace key env vars, and SDK baseUrl, including a secure env-file workflow and what still requires Agent Relay Cloud.

The root README Self Hosting blurb now links to that guide instead of only offering email support.

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Agent Relay sessions

• claude session 47b72585 · opened via gh pr create · last active 2026-10-13