feat(plugin): add the tether skill — email handoff for long-running sessions

[jiashuoz]

What

Adds a Beta tether skill to the e2a plugin. During a long-running coding session, the agent emails threaded status updates to the user as it sees fit and polls for emailed replies — so a user who's AFK can steer the agent from their inbox. Reply stop to end.

Architecture

Coding agents are turn-based; nothing native listens to an inbox mid-session. So the two directions use different mechanisms:

• Send = agent-driven — the agent calls tether.sh update "…" at meaningful moments (model's judgment sets cadence → no per-turn spam).
• Receive = poll-driven — tether.sh poll on an interval; keep the session alive with /loop so replies sent while idle are still picked up (no hook fires while idle).
• Blocked-alert = optional Notification hook — emails when the agent is stuck on a permission prompt.

Credentials

Reuses the CLI's agent creds from e2a login (~/.e2a/config.json) — no separate .env needed. Falls back to ~/.e2a-tether.env / env vars. Uses the static, agent-scoped CLI api_key (the right credential for shell/hook context; the MCP OAuth token is client-managed and not reusable here).

Files

file	role
skills/tether/tether.sh	runtime CLI: start / update / poll / status / stop
skills/tether/lib.sh	config + e2a send/reply/poll helpers
skills/tether/hooks/tether-notify.sh	optional Notification hook
skills/tether/install.sh	wire/unwire the hook; _selftest
skills/tether/tether.env.example	credentials template

Housekeeping

• Bumps plugin to 0.4.2 across all client + marketplace manifests (validator enforces parity).
• Lists agentify + tether in the README tree.

Testing

• node scripts/validate-plugin.mjs → 3 skills, version 0.4.2, manifests in sync.
• install.sh _selftest green (hooks no-op unconfigured; syntax OK).
• Offline end-to-end via stubbed curl: start → update → poll → stop with no duplicate reply reporting.

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