Batch E - New Capabilities

Relay health endpoint and headless invite/join for scripting.

ADR-E01: /healthz on Relay

Context: The relay server is a critical public-facing service. Monitoring systems need a health endpoint.

Alternatives considered:

• TCP port check only - Just verify the port is open. Rejected because it doesn’t verify the relay is actually functional.
• Full metrics endpoint - Prometheus-style. Planned for Batch H, but /healthz needed now for basic monitoring.

Decision: HTTP /healthz endpoint on configurable address (default 127.0.0.1:9090). Returns JSON with status, uptime_seconds, and connected_peers. Restricted to loopback by default - reverse proxy or SSH tunnel for remote access.

Consequences: Minimal information exposure (no peer IDs, no version, no protocol list in the health response - hardened in the post-phase audit). Loopback-only prevents information disclosure to the public internet.

Reference: https://github.com/shurlinet/shurli/blob/main/cmd/shurli/cmd_relay_serve.go

ADR-E02: Headless Invite/Join

Context: Docker containers, CI/CD pipelines, and scripts need to create/accept invites without interactive prompts or QR codes.

Alternatives considered:

• Separate CLI for scripting - A shurli-cli tool. Rejected because it fragments the tool.
• Environment variables only - SHURLI_INVITE_CODE=xxx shurli join. Supported alongside the flag.

Decision: --non-interactive flag on both invite and join. In non-interactive mode: invite prints bare code to stdout (progress to stderr), join reads code from positional arg or SHURLI_INVITE_CODE env var. No QR code, no prompts, no color.

Consequences: Docker integration tests can create and exchange invite codes programmatically. The flag reuses the same code paths as interactive mode - just different I/O routing.

Reference: https://github.com/shurlinet/shurli/blob/main/cmd/shurli/cmd_invite.go:34, https://github.com/shurlinet/shurli/blob/main/cmd/shurli/cmd_join.go